Acoustic sensor assembly

ABSTRACT

An acoustic sensor is configured to provide accurate and robust measurement of bodily sounds under a variety of conditions, such as in noisy environments or in situations in which stress, strain, or movement may be imparted onto a sensor with respect to a patient. Embodiments of the sensor provide a conformable electrical shielding, as well as improved acoustic and mechanical coupling between the sensor and the measurement site.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/643,939, filed Dec. 21, 2009, which application claims the benefit ofpriority from U.S. Provisional Application Nos. 61/141,584 filed Dec.30, 2008, and 61/252,076 filed Oct. 15, 2009. All of theabove-identified applications are hereby incorporated by referenceherein in their entireties and for all purposes.

BACKGROUND

1. Field

The present invention relates to non-invasive biological parametersensing, including sensing using acoustic sensors.

2. Description of the Related Art

The “piezoelectric effect” is the appearance of an electric potentialand current across certain faces of a crystal when it is subjected tomechanical stresses. Due to their capacity to convert mechanicaldeformation into an electric voltage, piezoelectric crystals have beenbroadly used in devices such as transducers, strain gauges andmicrophones. However, before the crystals can be used in many of theseapplications they must be rendered into a form which suits therequirements of the application. In many applications, especially thoseinvolving the conversion of acoustic waves into a corresponding electricsignal, piezoelectric membranes have been used.

Piezoelectric membranes are typically manufactured from polyvinylidenefluoride plastic film. The film is endowed with piezoelectric propertiesby stretching the plastic while it is placed under a high-polingvoltage. By stretching the film, the film is polarized and the molecularstructure of the plastic aligned. A thin layer of conductive metal(typically nickel-copper) is deposited on each side of the film to formelectrode coatings to which connectors can be attached.

Piezoelectric membranes have a number of attributes that make theminteresting for use in sound detection, including: a wide frequencyrange of between 0.001 Hz to 1 GHz; a low acoustical impedance close towater and human tissue; a high dielectric strength; a good mechanicalstrength; and piezoelectric membranes are moisture resistant and inertto many chemicals.

Due in large part to the above attributes, piezoelectric membranes areparticularly suited for the capture of acoustic waves and the conversionthereof into electric signals and, accordingly, have found applicationin the detection of body sounds. However, there is still a need for areliable acoustic sensor particularly suited for measuring bodily soundsin noisy environments.

SUMMARY

Embodiments of an acoustic sensor described herein are configured toprovide accurate and robust measurement of bodily sounds under a varietyof conditions, such as in noisy environments or in situations in whichstress, strain, or movement may be imparted onto sensor with respect toa patient. For example, embodiments of the sensor provide enhancedelectrical shielding, improved coupling between the sensor and themeasurement site, and robust physical connection between the sensor andthe patient, among other advantages.

The acoustic sensor can include an electrical shielding barrier, forexample, which provides for beneficial electrical shielding of a sensingelement, such as a piezoelectric element of the sensor, from externalelectrical noises. The electrical shielding barrier can include one ormore layers which form a Faraday cage around the piezoelectric element,for example, and which distribute external electrical noisesubstantially equally to first and second electrical poles of thepiezoelectric sensing element. In addition, the shielding barrierflexibly conforms to the surface shape of the piezoelectric element asthe surface shape of the piezoelectric element changes, therebyimproving the shielding and sensor performance.

Embodiments of the acoustic sensor also include an acoustic couplerwhich advantageously improves the coupling between the source of thesignal to be measured by the sensor (e.g., the patient's skin) and thesensing element. The acoustic coupler of one embodiment includes a bumppositioned to apply pressure to the sensing element to bias the sensingelement in tension. The acoustic coupler is further configured totransmit bodily sound waves to the sensing element. The acoustic couplercan also provide electrical isolation between the patient and theelectrical components of the sensor. Such isolation can beneficiallyprevent potentially harmful electrical pathways or ground loops fromforming and affecting the patient or the sensor.

An attachment element of the sensor may also be included which isconfigured to press the sensor against the patient's skin with apre-determined amount of force. The attachment element can include anelongate member including lateral extensions symmetrically placed aboutthe sensor such as wing-like extensions or arms that extend from thesensor. The elongate member can be made from a resilient, bendablematerial which rebounds readily after being bent or otherwise acts in aspring-like manner to press the sensor against the patient. Theattachment element can also be configured such that movement of thesensor with respect to the attachment element does not cause theattachment element to peel off or otherwise detach from the patientduring use.

In some embodiments, a cable assembly for use with an acoustic sensorincludes a patient anchor which advantageously secures the sensor to thepatient at a point between the ends of the cable. Securing the cable tothe patient can decouple movement of the cable due to various movementssuch as accidental yanking or jerking on the cable or movement of thepatient. Decoupling the sensor from cable movement can significantlyimprove performance by eliminating or reducing acoustical noiseassociated with cable movement. For example, by decoupling the sensorfrom cable movement, cable movement will not register or otherwise beintroduced as noise in the acoustical signal generated by the sensor.

While some aspects of the disclosure are often described separatelyherein, various aspects can be combined in certain embodiment to providesynergistic results. While a variety of beneficial combinations arepossible, as one example, attachment elements described herein can beused in conjunction with the acoustic couplers, e.g., to provideimproved coupling between the signal and the sensor. Patient anchors andattachment elements can combine to ensure that the sensor assemblyremains securely attached to the patient during use.

The sensor of certain embodiments is resposable and includes bothreusable and disposable elements. For example, in certain embodiments,the sensor includes a reusable sensor portion and a disposableattachment portion. In one embodiment, the reusable elements may includethose components of the sensor that are more expensive such as thesensing components and other electrical components of the sensor. Thedisposable elements, on the other hand, may include those components ofthe sensor that are relatively less expensive, such as, for example,tape portions, bandages, or other mechanisms for removably attaching thesensor to a measurement site. For example, the disposable portion mayinclude one of the attachment elements described herein and the reusableportion may include the sensor subassemblies described herein.Additional information relating to resposable sensors compatible withembodiments described herein may be found in U.S. Pat. No. 6,920,345,filed Jan. 24, 2003, entitled “Optical Sensor Including Disposable andReusable Elements,” (hereinafter referred to as “the '345 patent”),which is incorporated in its entirety by reference herein.

An acoustic sensor assembly is provided for non-invasively outputting asignal responsive to acoustic vibrations indicative of one or morephysiological parameters of a medical patient. The sensor assemblyincludes a frame and a first electrical shielding layer supported by theframe. The sensor assembly can further include a sensing elementconfigured to output a signal responsive to acoustic vibrations. In someembodiments, the sensing element comprises a piezoelectric film. Thesensing element can be supported by the frame and, in certainembodiments, the first electrical shielding layer is positioned betweenthe frame and the sensing element. The sensor assembly can also includea second electrical shielding layer supported by the frame. In someembodiments, the sensing element positioned between the secondelectrical shielding element and the frame. The second electricalshielding layer can also be configured to conform to a surface shape ofthe sensing element as the sensing element surface moves in response tosaid acoustic vibrations. In certain embodiments, the first electricalshielding layer is configured to conform to the surface the sensingelement as the sensing element moves in response to said acousticvibrations. Additionally, the first and second electrical shieldinglayers form a Faraday cage around the sensing element in someembodiments.

In certain embodiments, the sensing element comprises first and secondelectrical poles, and the first and second electrical shielding layersdistribute electrical noise directed to the shielding elementsubstantially equally to the first and second electrical poles. Theshielding layers can be configured to distribute electrical noisesubstantially in phase to the first and second electrical poles, forexample. In some embodiments, the sensing element and first and secondshielding layers are configured to substantially shield noise bycommon-mode rejection. According to certain embodiments, the electricalshielding element is configured to improve noise immunity of theacoustic sensor assembly. The electrical shielding element can also beconfigured to lower a noise component of an output signal generated bythe acoustic sensor assembly. The electrical shielding element canadditionally be configured to provide an improved signal-to-noise ratio.

One or more of the first and second electrical shielding layers comprisecopper in certain embodiments. One or more of the first and secondelectrical shielding layers can be from between about 0.5 micrometer andabout 10 micrometers thick, for example. In one embodiment, one or moreof the first and second electrical shielding layers are approximately 3micrometers thick.

The acoustic sensor assembly may further include an insulating layerpositioned between the sensing element and the first shielding layer. Asecond insulating layer can be positioned between the sensing elementand the second shielding layer in some embodiments. The insulating layercan comprise an adhesive, for example.

According to another aspect of the disclosure, an acoustic sensorassembly is provided for non-invasively outputting a signal responsiveto acoustic vibrations indicative of one or more physiologicalparameters of a medical patient. The sensor assembly includes a frameand a sensing element configured to output a signal responsive toacoustic vibrations and supported by the frame, the sensing elementcomprising a first electrical pole and a second electrical pole. Thesensor assembly also includes an electrical shielding element supportedby the frame and positioned relative to the sensing element, wherein theelectrical shielding element distributes noise directed to the sensingelement substantially equally to the first and second electrical poles.

According to certain embodiments, the electrical shielding element formsa faraday cage with respect to the sensing element. Additionally, theelectrical shielding element can distribute a first portion of theelectrical noise to the first electrical pole and a second portion ofthe electrical noise to the second electrical pole, wherein the firstand second noise portions are substantially in phase with each other,for example. The electrical shielding element may be configured toremove noise by common-mode rejection. In some embodiments, theelectrical shielding element is configured to lower a noise component ofan output signal generated by the acoustic sensor assembly.

In some embodiments, the electrical shielding element includes a firstlayer and a second layer, and the sensing element is positioned betweenthe first layer and the second layer. The electrical shielding elementis from between about 0.5 micrometer and about 10 micrometers thick incertain embodiments. In some embodiments, the electrical shieldingelement is approximately 3 micrometers thick. At least a portion of theelectrical shielding element conforms to a surface of the sensingelement during use in certain embodiments.

In yet other embodiments, a method of manufacturing a shielded acousticsensor includes attaching a first electrical shielding layer to a frame.The method can further include attaching a sensing layer to the frameand over the first electrical shielding layer. The method may alsoinclude attaching a second electrical shielding layer to the frame andover the sensing layer, wherein said second electrical shielding layeris configured to conform to a surface defined by the sensing layer asthe sensing layer surface changes shape.

In another embodiment, a method of manufacturing a shielded acousticsensor includes attaching a sensing element configured to output asignal responsive to acoustic vibrations to a frame, the sensing elementcomprising a first electrical pole and a second electrical pole. Incertain embodiments, the method includes and positioning an electricalshielding element relative to the sensing element, wherein theelectrical shielding element distributes noise directed to the sensingelement substantially equally to the first and second electrical poles.

According to another aspect of the disclosure, an acoustic sensorassembly for non-invasively outputting a signal responsive to acousticvibrations indicative of one or more physiological parameters of amedical patient includes a frame. The sensor assembly can also include asensing element configured to output a signal responsive to acousticvibrations and supported by the frame. The sensor assembly can alsoinclude and an acoustic coupler supported by the frame and positioned toapply pressure to the sensing element to bias the sensing element at apredetermined tension. The acoustic coupler can be configured totransmit acoustic vibrations to the sensing element through the acousticcoupler when the acoustic sensor assembly is attached to the medicalpatient.

The acoustic coupler can include an inner protrusion disposed on aninside surface of the acoustic coupler. In some embodiments, theacoustic coupler further comprises an outer protrusion disposed on anoutside surface of the acoustic coupler.

Additionally, the acoustic coupler can electrically insulate theacoustic sensing element from the medical patient when the acousticsensor assembly is attached to the medical patient. According to someembodiments, the acoustic coupler electrically isolates the acousticsensing element from the medical patient when the acoustic sensorassembly is attached to the medical patient. The acoustic couplercomprises an elastomer in some embodiments.

The acoustic coupler can be configured to substantially evenlydistribute pressure on the sensing element, for example. The sensingelement can comprises a piezoelectric material. In certain embodiments,the acoustic coupler comprises a gel. The gel according to someembodiments provides acoustic impedance matching between a measurementsite of the patient and the sensing element.

The acoustic sensor assembly may further include an information elementsupported by the frame. The information element is configured to storeone or more of sensor use information, sensor compatibility information,and sensor calibration information, for example. The acoustic sensorassembly can further include a cable in communication with the sensingelement and a connector attached to the cable, wherein the informationelement is supported by the connector. In some embodiments, theinformation element comprises one or more memory devices. The acousticsensor assembly can further include an attachment element configured toapply a predetermined force to the frame during use, further improvingthe coupling between the signal and the sensing element.

A method of manufacturing an acoustic sensor is provided in certainembodiments. The method can include providing an acoustic coupler, asensing element, and a frame, the frame defining an open cavity. Themethod can further include attaching the sensing element to the framesuch that the sensing layer extends across the open cavity. In certainembodiments, the method also include attaching the acoustic coupler tothe frame. The acoustic coupler applies pressure to the sensing elementto bias the sensing element at a predetermined tension, for example.Additionally, the acoustic coupler is configured to transmit acousticvibrations to the sensing element through the acoustic coupler when theacoustic sensor assembly is attached to a medical patient.

In another embodiment, a method of non-invasively outputting a signalresponsive to acoustic vibrations indicative of one or morephysiological parameters of a medical patient includes providing anacoustic sensor, the acoustic sensor comprising a frame, a sensingelement configured to detect acoustic vibrations and supported by theframe, and an acoustic coupler supported by the frame and positioned toapply pressure to the sensing element so as to bias the sensing elementto a predetermined tension prior to attachment to a medical patient. Themethod can further include attaching the acoustic sensor to the medicalpatient wherein the acoustic coupler is placed in contact with themedical patient. The method can further include outputting a signalresponsive to acoustic vibrations indicative of a physiologicalparameter of the medical patient based on acoustic vibrationstransmitted through the acoustic coupler and detected by the sensingelement. In some embodiments, the attaching further includes using anattachment assembly of the acoustic sensor configured to apply apredetermined force to the frame, wherein the acoustic sensor is pressedagainst the medical patient.

In another embodiment, an acoustic sensor assembly is provided fornon-invasively outputting a signal responsive to acoustic vibrationsindicative of one or more physiological parameters of a medical patient,including a frame and a sensing element supported by the frame andconfigured to detect acoustic vibrations from the medical patient andprovide an output signal indicative of the acoustic vibrations. Thesensor assembly can further include an elongate member supported by theframe, the elongate member comprising a spring portion extending atleast partially beyond opposite sides of the frame. The elongate membercan be configured to apply a predetermined force to the frame with thespring portion, wherein the acoustic sensor assembly is pressed againsta measurement site of the medical patient when the acoustic sensorassembly is attached to the medical patient. The predetermined force canbe determined at least in part based upon a stiffness of the springportion.

The elongate member is substantially flat when the acoustic sensorassembly is not attached to the medical patient in some embodiments.Additionally, the elongate member may bend away from the frame when theacoustic sensor assembly is not attached to the medical patient.

In certain embodiments, the frame can include a top surface and a bottomsurface, the sensing element extending across the bottom surface, andthe elongate member extending across and beyond the top surface. Theelongate member can be coupled to a middle portion of the frame, forexample. In some embodiments, the acoustic sensor assembly furtherincludes a dielectric material supported by the frame and positionedbetween the frame and the elongate member. Additionally, the elongatemember may be configured to apply continuous force on the frame to pressit into the medical patient's skin as the medical patient's skinstretches.

The elongate member according to some embodiments further includes anattachment portion configured to attach the acoustic sensor assembly tothe patient. The attachment portion comprises an adhesive, for example.The elongate member can be removably coupled to the frame, be disposableand/or have a forked shape according to various embodiments.

An acoustic sensor assembly is provided for non-invasively outputting asignal responsive to acoustic vibrations indicative of one or morephysiological parameters of a medical patient. The sensor assemblyincludes a frame and a sensing element supported by the frame. Thesensor assembly can be configured to provide a signal indicative ofacoustic vibrations detected by the sensing element. The sensor assemblycan further include an attachment element supported by the frame,including an attachment layer, configured to secure the acoustic sensorassembly to the medical patient. The attachment element may furtherinclude an elongate member comprising a resilient material wherein theelongate member is movably coupled to the attachment layer. The elongatemember can be configured to move from a first position in which theelongate member is substantially parallel to the attachment layer to asecond position in which the elongate member is inclined at an anglewith respect to the attachment layer when the attachment layer isattached to the medical patient.

An end of the elongate member is positioned a predetermined distancefrom an edge of the attachment layer in some embodiments. The end of theelongate member can be positioned near the attachment layer's center,for example. The elongate member can be connected to the attachmentlayer wherein movement of the frame with respect to the attachment layerdoes not cause the attachment layer to detach from the medical patientduring use. The elongate member may be configured to apply apredetermined force on the frame to press the acoustic sensor assemblyagainst a measurement site of the medical patient during use, forexample. In certain embodiments, the attachment layer comprises anadhesive. The attachment element can also be removably coupled to theframe. In certain embodiments, the attachment element is disposable, forexample. In one embodiment, the elongate member comprises a forkedshape.

In another aspect of the disclosure, a method of attaching an acousticsensor assembly for non-invasively sensing one or more physiologicalparameters to a medical patient includes providing an acoustic sensorassembly comprising a frame. The sensor assembly can also include asensing element supported by the frame. The elongate member can besupported by the frame and can include a spring portion extending atleast partially beyond opposite sides of the frame. The method canfurther include attaching the acoustic sensor assembly to a medicalpatient by attaching the elongate member to the medical patient's skin.The method can also include applying a predetermined force to the framewith the spring portion, wherein the acoustic sensor assembly is pressedagainst the medical patient's skin, wherein the predetermined force isdetermined at least in part based upon a stiffness of the springportion.

In yet another embodiment, a method of attaching an acoustic sensorassembly for non-invasively sensing one or more physiological parametersto a medical patient can includes providing an acoustic sensor assemblycomprising a frame, a sensing element supported by the frame, and anattachment element supported by the frame. The attachment element caninclude an attachment layer which can be configured to secure theacoustic sensor assembly to the medical patient. An elongate member canbe included comprising a resilient material and coupled to theattachment layer. The method can also include attaching the acousticsensor assembly to a medical patient by attaching the attachment layerto the medical patient's skin. The attaching of the attachment layer caninclude bending the elongate member from a first position in which theelongate member is substantially parallel to the attachment layer to asecond position in which the elongate member is inclined at an anglewith respect to the attachment layer.

In another embodiment, an acoustic sensor assembly is provided includinga frame and a sensing element, supported by the frame. The sensorassembly can further include a resilient backbone extending across andbeyond opposite sides of the frame. An attachment element can beprovided at outside ends of said backbone can include top and bottomportions. The top portion can be attached to the backbone, and thebottom portion can be configured to attach to a medical patient, forexample. The top portion can also be configured to be inclined withrespect to said bottom portion when attached to said medical patient.

In another embodiment, a cable assembly for use with a sensor configuredto sense one or more physiological parameters of a medical patient isprovided. The cable assembly can include a connector and a cable, forexample. The cable can have a proximal end attached to the connector anda distal end. The distal end can be configured to attach to a sensoradapted to output a signal responsive to acoustic vibrations from amedical patient. The cable assembly can also include a patient anchorattached to the cable between the proximal end and the distal end. Thepatient anchor can be configured to attach to the patient at ananchoring site and to secure the cable to the patient with respect tothe anchoring site, for example.

The patient anchor can be configured to decouple movement of the cableproximal end from the cable distal end when the patient anchor isattached to the patient. Additionally, the cable can further include abent portion located at the patient anchor. The bent portion forms an“S” shape in some embodiments. The patient anchor comprises an adhesivein some embodiments. The cable assembly can also be removably coupled tothe sensor. The patient anchor can be configured to be attached to themedical patient's neck.

In another embodiment, a method of securing a non-invasive physiologicalsensor to a measurement site on a medical patient includes providing asensor assembly. The sensor assembly can have a sensor and a cable, forexample. The sensor can also have a patient attachment portion. Thecable may have first end, a second end, and an anchor located betweenthe first and second ends. The method can further include attaching thesensor to a measurement site on the medical patient with the patientattachment portion. The method of certain embodiments also includesattaching the cable to an anchoring site on the medical patient with theanchor. The attaching the sensor can include attaching the sensor to themeasurement site with an adhesive located on the patient attachmentportion. Additionally, the attaching the cable can include attaching thecable to the anchoring site with an adhesive located on the anchor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B are block diagrams illustrating physiological monitoringsystems in accordance with embodiments of the disclosure;

FIG. 2A is a top perspective view illustrating portions of a sensorassembly in accordance with an embodiment of the disclosure;

FIGS. 2B-C are top and bottom perspective views, respectively, of asensor including a sensor subassembly and an attachment subassembly ofFIG. 2A;

FIGS. 2D-2E are top and bottom exploded, perspective views,respectively, of the sensor subassembly of FIGS. 2A-C;

FIG. 2F shows a top perspective view of an embodiment of a supportframe;

FIG. 3A a perspective view of a sensing element according to anembodiment of the disclosure usable with the sensor assembly of FIG. 2A;

FIG. 3B is a cross-sectional view of the sensing element of FIG. 3Aalong the line 3B-3B;

FIG. 3C is a cross-sectional view of the sensing element of FIGS. 3A-Bshown in a wrapped configuration;

FIG. 4 is a cross-sectional view of the coupler of FIGS. 2A-2E takenalong the line 4-4 shown in FIG. 2D;

FIG. 5A-B are cross-sectional views of the sensor subassembly of FIGS.2-3 along the lines 5A-5A and 5B-5B, respectively;

FIG. 6A is a top perspective view illustrating portions of a sensorassembly in accordance with another embodiment of the disclosure;

FIG. 6B-C are top and bottom perspective views, respectively, of asensor including a sensor subassembly and an attachment subassembly ofFIG. 6A;

FIG. 6D-E are top and bottom exploded, perspective views, respectively,of the sensor subassembly of FIGS. 6A-C;

FIG. 7 illustrates a block diagram of an information element accordingto embodiments of the disclosure;

FIG. 8 illustrates a flowchart of one embodiment of a sensor lifemonitoring method;

FIG. 9A is a perspective, exploded view of an attachment subassemblycompatible with any of the sensor assemblies of FIGS. 1A-2E and 6A-6Eaccording to an embodiment of the disclosure;

FIG. 9B is a side view of a sensor subassembly that includes theattachment subassembly of FIG. 9A according to embodiments of thedisclosure;

FIGS. 9C-D show an embodiment of a attachment subassembly whenunattached and attached to a measurement site, respectively;

FIG. 10 is a perspective, exploded view of an attachment subassemblycompatible with any of the sensor assemblies of FIGS. 1A-2E and 6A-6Eaccording to another embodiment of the disclosure;

FIG. 11A is a perspective view of a patient anchor compatible with anyof the sensor assemblies of FIGS. 1A-2E and 6A-6E according to anembodiment of the disclosure;

FIG. 11B is a perspective, exploded view of the patient anchor of FIG.10A; and

FIG. 12 is a top view of a patient anchor and a sensor subassemblyattached to a patient according to embodiments of the disclosure.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. These embodiments are illustrated and describedby example only, and are not intended to be limiting.

In various embodiments, an acoustic sensor configured to operate with aphysiological monitoring system includes an acoustic signal processingsystem that measures and/or determines any of a variety of physiologicalparameters of a medical patient. For example, in an embodiment, thephysiological monitoring system includes an acoustic monitor. Forexample, the acoustic monitor may be an acoustic respiratory monitorwhich can determine any of a variety of respiratory parameters of apatient, including respiratory rate, expiratory flow, tidal volume,minute volume, apnea duration, breath sounds, riles, rhonchi, stridor,and changes in breath sounds such as decreased volume or change inairflow. In addition, in some cases the acoustic signal processingsystem monitors other physiological sounds, such as heart rate to helpwith probe off detection, heart sounds (S1, S2, S3, S4, and murmurs),and change in heart sounds such as normal to murmur or split heartsounds indicating fluid overload. Moreover, the acoustic signalprocessing system may (1) use a second probe over the chest foradditional heart sound detection; (2) keep the user inputs to a minimum(example, height); and/or (3) use a Health Level 7 (HL7) interface toautomatically input patient demography.

In certain embodiments, the physiological monitoring system includes anelectrocardiograph (ECG or EKG) that measures and/or determineselectrical signals generated by the cardiac system of a patient. The ECGincludes one or more sensors for measuring the electrical signals. Insome embodiments, the electrical signals are obtained using the samesensors used to obtain acoustic signals.

In still other embodiments, the physiological monitoring system includesone or more additional sensors used to determine other desiredphysiological parameters. For example, in some embodiments, aphotoplethysmograph sensor determines the concentrations of analytescontained in the patient's blood, such as oxyhemoglobin,carboxyhemoglobin, methemoglobin, other dyshemoglobins, totalhemoglobin, fractional oxygen saturation, glucose, bilirubin, and/orother analytes. In other embodiments, a capnograph determines the carbondioxide content in inspired and expired air from a patient. In otherembodiments, other sensors determine blood pressure, pressure sensors,flow rate, air flow, and fluid flow (first derivative of pressure).Other sensors may include a pneumotachometer for measuring air flow anda respiratory effort belt. In certain embodiments, these sensors arecombined in a single processing system which processes signal outputfrom the sensors on a single multi-function circuit board.

FIG. 1A illustrates an embodiment of a physiological monitoring system100. A medical patient 101 is monitored using one or more sensorassemblies 103, each of which transmits a signal over a cable 105 orother communication link or medium to a physiological monitor 107. Thephysiological monitor 107 includes a processor 109 and, optionally, adisplay 111. The one or more sensors 103 include sensing elements suchas, for example, acoustic piezoelectric devices, electrical ECG leads,or the like. The sensors 103 generate respective signals by measuring aphysiological parameter of the patient 101. The signal is then processedby one or more processors 109. The one or more processors 109 thencommunicate the processed signal to the display 111. In an embodiment,the display 111 is incorporated in the physiological monitor 107. Inanother embodiment, the display 111 is separate from the physiologicalmonitor 107. In one embodiment, the monitoring system 100 is a portablemonitoring system.

For clarity, a single block is used to illustrate the one or moresensors 103 shown in FIG. 1A. It should be understood that the sensor103 block shown is intended to represent one or more sensors. In anembodiment, the one or more sensors 103 include a single sensor of oneof the types described below. In another embodiment, the one or moresensors 103 include at least two acoustic sensors. In still anotherembodiment, the one or more sensors 103 include at least two acousticsensors and one or more ECG sensors. In each of the foregoingembodiments, additional sensors of different types are also optionallyincluded. Other combinations of numbers and types of sensors are alsosuitable for use with the physiological monitoring system 100.

In some embodiments of the system shown in FIG. 1A, all of the hardwareused to receive and process signals from the sensors are housed withinthe same housing. In other embodiments, some of the hardware used toreceive and process signals is housed within a separate housing. Inaddition, the physiological monitor 107 of certain embodiments includeshardware, software, or both hardware and software, whether in onehousing or multiple housings, used to receive and process the signalstransmitted by the sensors 103.

As shown in FIG. 1B, the acoustic sensor assembly 103 can include acable 115 or lead. The cable 115 typically carries three conductorswithin an electrical shielding: one conductor 116 to provide power to aphysiological monitor 107, one conductor 118 to provide a ground signalto the physiological monitor 107, and one conductor 118 to transmitsignals from the sensor 103 to the physiological monitor 107. In someembodiments, the “ground signal” is an earth ground, but in otherembodiments, the “ground signal” is a patient ground, sometimes referredto as a patient reference, a patient reference signal, a return, or apatient return. In some embodiments, the cable 115 carries twoconductors within an electrical shielding layer, and the shielding layeracts as the ground conductor. Electrical interfaces 117 in the cable 115enable the cable to electrically connect to electrical interfaces 119 ina connector 120 of the physiological monitor 107. In another embodiment,the sensor assembly 103 and the physiological monitor 107 communicatewirelessly. Additional information relating to acoustic sensorscompatible with embodiments described herein, including otherembodiments of interfaces with the physiological monitor, are includedin U.S. patent application Ser. No. 12/044,883, filed Mar. 7, 2008,entitled “Systems and Methods for Determining a Physiological ConditionUsing an Acoustic Monitor,” (hereinafter referred to as “the '883Application”) which is incorporated in its entirety by reference herein.

FIG. 2A is a top perspective of a sensor system 200 including a sensorassembly 201 suitable for use with any of the physiological monitorsshown in FIGS. 1A-C and a monitor cable 211. The sensor assembly 201includes a sensor 215, a cable assembly 217 and a connector 205. Thesensor 215, in one embodiment, includes a sensor subassembly 202 and anattachment subassembly 204. The cable assembly 217 of one embodimentincludes a cable 207 and a patient anchor 203. The various componentsare connected to one another via the sensor cable 207. The sensorconnector subassembly 205 can be removably attached to monitor connector209 which is connected to physiological monitor (not shown) through themonitor cable 211. In one embodiment, the sensor assembly 201communicates with the physiological monitor wirelessly. In variousembodiments, not all of the components illustrated in FIG. 2A areincluded in the sensor system 200. For example, in various embodiments,one or more of the patient anchor 203 and the attachment subassembly 204are not included. In one embodiment, for example, a bandage or tape isused instead of the attachment subassembly 204 to attach the sensorsubassembly 202 to the measurement site. Moreover, such bandages ortapes may be a variety of different shapes including generally elongate,circular and oval, for example.

The sensor connector subassembly 205 and monitor connector 209 may beadvantageously configured to allow the sensor connector 205 to bestraightforwardly and efficiently joined with and detached from themonitor connector 209. Embodiments of sensor and monitor connectorshaving similar connection mechanisms are described in U.S. patentapplication Ser. No. 12/248,856 (hereinafter referred to as “the '856Application”), filed on Oct. 9, 2008, which is incorporated in itsentirety by reference herein. For example, the sensor connector 205includes a mating feature 213 which mates with a corresponding feature(not shown) on the monitor connector 209. The mating feature 205 mayinclude a protrusion which engages in a snap fit with a recess on themonitor connector 209. In certain embodiments, the sensor connector 205can be detached via one hand operation, for example. Examples ofconnection mechanisms may be found specifically in paragraphs [0042],[0050], [0051], [0061]-[0068] and [0079], and with respect to FIGS.8A-F, 13A-E, 19A-F, 23A-D and 24A-C of the '856 Application, forexample. The sensor system 200 measures one or more physiologicalparameters of the patient, such as one of the physiological parametersdescribed above.

The sensor connector subassembly 205 and monitor connector 209 mayadvantageously reduce the amount of unshielded area in and generallyprovide enhanced shielding of the electrical connection between thesensor and monitor in certain embodiments. Examples of such shieldingmechanisms are disclosed in the '856 Application in paragraphs[0043]-[0053], [0060] and with respect to FIGS. 9A-C, 11A-E, 13A-E,14A-B, 15A-C, and 16A-E, for example.

As will be described in greater detail herein, in an embodiment, theacoustic sensor assembly 201 includes a sensing element, such as, forexample, a piezoelectric device or other acoustic sensing device. Thesensing element generates a voltage that is responsive to vibrationsgenerated by the patient, and the sensor includes circuitry to transmitthe voltage generated by the sensing element to a processor forprocessing. In an embodiment, the acoustic sensor assembly 201 includescircuitry for detecting and transmitting information related tobiological sounds to a physiological monitor. These biological soundsmay include heart, breathing, and/or digestive system sounds, inaddition to many other physiological phenomena. The acoustic sensor 215in certain embodiments is a biological sound sensor, such as the sensorsdescribed herein. In some embodiments, the biological sound sensor isone of the sensors such as those described in the '883 Application. Inother embodiments, the acoustic sensor 215 is a biological sound sensorsuch as those described in U.S. Pat. No. 6,661,161, which isincorporated by reference herein. Other embodiments include othersuitable acoustic sensors.

The attachment sub-assembly 204 includes first and second elongateportions 206, 208. The first and second elongate portions 206, 208 caninclude patient adhesive (e.g., in some embodiments, tape, glue, asuction device, etc.) attached to a elongate member 210. The adhesive onthe elongate portions 206, 208 can be used to secure the sensorsubassembly 202 to a patient's skin. As will be discussed in greaterdetail herein, the elongate member 210 can beneficially bias the sensorsubassembly 202 in tension against the patient's skin and reduce stresson the connection between the patient adhesive and the skin. A removablebacking can be provided with the patient adhesive to protect theadhesive surface prior to affixing to a patient's skin.

The sensor cable 207 is electrically coupled to the sensor subassembly202 via a printed circuit board (“PCB”) (not shown) in the sensorsubassembly 202. Through this contact, electrical signals arecommunicated from the multi-parameter sensor subassembly to thephysiological monitor through the sensor cable 207 and the cable 211.

FIGS. 2B-C are top and bottom perspective views of a sensor includingsubassembly 202 and an attachment subassembly 204 in accordance with anembodiment of the present disclosure. The attachment subassembly 204generally includes lateral extensions symmetrically placed about thesensor subassembly 202. For example, the attachment subassembly 204 caninclude single, dual or multiple wing-like extensions or arms thatextend from the sensor subassembly 202. In other embodiments, theattachment subassembly 202 has a circular or rounded shape, whichadvantageously allows uniform adhesion of the attachment subassembly 204to an acoustic measurement site. The attachment subassembly 204 caninclude plastic, metal or any resilient material, including a spring orother material biased to retain its shape when bent. In the illustratedembodiment, the attachment subassembly 204 includes a first elongateportion 206, a second elongate portion 208, an elongate member 210 and abutton 212. As will be discussed, in certain embodiments the attachmentsubassembly 204 or portions thereof are disposable and/or removablyattachable from the sensor subassembly 202. The button 210 mechanicallycouples the attachment subassembly 204 to the sensor subassembly 202.The attachment subassembly 204 is described in greater detail below withrespect to FIGS. 9A-9D. The attachment subassembly 204 may also bereferred to as an attachment element herein.

In one embodiment, the sensor subassembly 202 is configured to beattached to a patient and includes a sensing element configured todetect bodily sounds from a patient measurement site. The sensingelement may include a piezoelectric membrane, for example, and issupported by a support structure such as a generally rectangular supportframe 218. The piezoelectric membrane is configured to move on the framein response to acoustic vibrations, thereby generating electricalsignals indicative of the bodily sounds of the patient. An electricalshielding barrier (not shown) may be included which conforms to thecontours and movements of the piezoelectric element during use. In theillustrated embodiment, additional layers are provided to help adherethe piezoelectric membrane to the electrical shielding barrier 227.Embodiments of the electrical shielding barrier are described below withrespect to FIGS. 3A-B and FIGS. 5A-B, for example.

Embodiments of the sensor subassembly 202 also include an acousticcoupler, which advantageously improves the coupling between the sourceof the signal to be measured by the sensor (e.g., the patient's skin)and the sensing element. The acoustic coupler of one embodiment includesa bump positioned to apply pressure to the sensing element so as to biasthe sensing element in tension. The acoustic coupler can also provideelectrical isolation between the patient and the electrical componentsof the sensor, beneficially preventing potentially harmful electricalpathways or ground loops from forming and affecting the patient or thesensor.

The sensor subassembly 202 of the illustrated embodiment includes anacoustic coupler 214 which generally envelops or at least partiallycovers some or all of the components the other components of the sensorsubassembly 202. Referring to FIG. 2C, the bottom of the acousticcoupler 214 includes a contact portion 216 which is brought into contactwith the skin of the patient. Embodiments of acoustic couplers aredescribed below with respect to FIGS. 2D-E, 4, and 5A-B, for example.

FIGS. 2D-E are top and bottom exploded, perspective views, respectively,of the sensor subassembly 202 of FIGS. 2A-C.

Support Frame

The frame generally supports the various components of the sensor. Forexample, the piezoelectric element, electrical shielding barrier,attachment element and other components may be attached to the frame.The frame can be configured to hold the various components in place withrespect to the frame and with respect to one another, therebybeneficially providing continuous operation of the sensor under avariety of conditions, such as during movement of the sensor. Forexample, the frame can be configured to hold one or more of thecomponents together with a predetermined force. Moreover, the frame caninclude one or more features which can improve the operation of thesensor. For example, the frame can include one or more cavities whichallow for the piezoelectric element to move freely and/or which amplifyacoustic vibrations from bodily sounds of the patient.

In the illustrated embodiment, a PCB 222 is mounted on the frame 218.The frame 218 supports a series of layers which are generally wrappedaround the underside 242 of the frame 218 and include, from innermost tooutermost, an inner shield layer 226, an bonding layer 224, a sensingelement 220 and an outer shield layer 228.

As shown in FIG. 2D, the support frame 218 has a generally rectangularshape, as viewed from the top or bottom, although the frame shape couldbe any shape, including square, oval, elliptical, elongated, etc. Invarious embodiments, the frame 218 has a length of from between about 5and 50 millimeters. In one embodiment, the frame 218 has a length ofabout 17 millimeters. The relatively small size of the frame 218 canallow the sensor subassembly 202 to be attached comfortably tocontoured, generally curved portions of the patient's body. For,example, the sensor subassembly 202 can be comfortably attached toportions of the patient's neck whereas a larger frame 218 may beawkwardly situated on the patient's neck or other contoured portion ofthe patient. The size of the frame 218 may allow for the sensorsubassembly 202 to be attached to the patient in a manner allowing forimproved sensor operation. For example, the relatively small frame 218,corresponding to a relatively smaller patient contact area, allows forthe sensor subassembly 202 to be applied with substantially uniformpressure across the patient contact area.

The frame 218 is configured to hold the various components in place withrespect to the frame. For example, in one embodiment, the frame 218includes at least one locking post 232, which is used to lock the PCB222 into the sensor sub-assembly 202, as described below. In theillustrated embodiment, the frame 218 includes four locking posts 232,for example, near each of the 218 four corners of the frame 218. Inother embodiments, the frame 218 includes one, two, or three lockingposts 218. When the locking posts 232 are brought into contact withhorns of an ultrasonic welder or a heat source, they liquefy and flow toexpand over the material beneath it and then harden in the expandedstate when the welder is removed. When the components of the sensorsub-assembly 202 are in place, the locking posts 232 are flowed to lockall components into a fixed position.

In one embodiment, the locking posts 232 are formed from the samematerial as, and are integral with the frame 218. In other embodiments,the locking posts 232 are not formed from the same material as the frame218. For example, in other embodiments, the locking posts 232 includeclips, welds, adhesives, and/or other locks to hold the components ofthe sensor sub-assembly 202 in place when the locking posts 232 arelocked into place.

With further reference to FIG. 2E, in an assembled configuration, thePCB 222 sits inside of an upper cavity 230 of the frame 218 and ispressed against the sensing element 220 to create a stable electricalcontact between the PCB 222 and electrical contact portions of thesensing element 220. For example, in certain embodiments, the expandedlocking posts 232 press downward on the PCB 222 against the sensingelement 220, which is positioned between the PCB 222 and the frame 218.In this manner, a stable and sufficient contact force between the PCB222 and the sensing element 220 is maintained. For example, as thesensor assembly 200 moves due to acoustic vibrations coming from thepatient or due to other movements of the patient, the electrical contactbetween the PCB 222 and the sensing element 220 remains stable,constant, uninterrupted, and/or unchanged.

In another embodiment, the sensing element 220 may be positioned overthe PCB 222 between the expanded locking posts 232 and the PCB 222. Incertain embodiments, the contact force between the PCB 222 and thesensing element 220 is from between about 0.5 pounds and about 10pounds. In other embodiments, the contact force is between about 1 poundand about 3 pounds. In one embodiment, the contact force between the PCB222 and the sensing element 220 is at least about 2 pounds. The bondinglayer 224 is positioned between the frame 218 and the sensing element220 and allows, among other things, for the sensing element 220 to beheld in place with respect to the frame 218 prior to placement of thePCB 222. The PCB 222 and frame 218 include corresponding cutout portions246, 248 which are configured to accept the sensor cable (not shown).

The PCB cutout portion 246 also includes a circular portion which isconfigured to accept a button post 244 positioned in the center of thecavity 230. The button post 244 is configured to receive the button 212(FIG. 2B). The frame 218, shielding layers 226, 228, adhesive layer 224,and sensing element 220 each include injection holes 235 extendingthrough opposing sides of the respective components. Additionally, in anassembled configuration the injection holes 235 of the variouscomponents line up with the holes 235 of the other components such thata syringe or other device can be inserted through the holes. Glue isinjected into the holes 235 using the syringe, bonding the assembledcomponents together.

Referring now to FIG. 2E, a lower cavity 236 is disposed on theunderside of the frame 218 and has a depth d. In an assembledconfiguration, the sensing element 220 is wrapped around the frame 218in the direction of the transverse axis 238 such that the lower planarportion 262 of the sensing element 220 stretches across the top of thelower cavity 236. As such, the lower cavity 236 can serve as an acousticchamber of the multi-parameter sensor assembly. The sensing element 220thus has freedom to move up into the acoustic chamber in response toacoustic vibrations, allowing for the mechanical deformation of thepiezoelectric sensing material and generation of the correspondingelectrical signal. In addition, the chamber of certain embodimentsallows sound waves incident on the sensing element to reverberate in thechamber. As such, the sound waves from the patient may be amplified ormore effectively directed to the sensing element 220, thereby improvingthe sensitivity of the sensing element 220. As such, the cavity 236allows for improved operation of the sensor.

The frame may include one or more contacts extending from the framewhich press into corresponding contact strips of the PCB, helping toensure a stable, relatively constant contact resistance between the PCBand the sensing element. FIG. 2F shows a top perspective view of anotherembodiment of a support frame 318, which includes such contacts. Theframe 318 may be generally similar in structure and include one or moreof the features of the frame 218, such as the locking posts 332 and theupper surface 384. The frame 318 further includes one or more contactbumps 320 which press into corresponding contact strips 223 (FIG. 3B) ofthe PCB 222 when the sensor sub-assembly is assembled. For example, thecontact bumps 320 may include generally narrow rectangular raisedsegments and may be positioned on the upper surface 384 of the frame318.

The contact bumps 320 help ensure a stable, constant contact resistancebetween the PCB 222 and the sensing element 220. The contact bumps 320are dimensioned to press a portion of the sensing element 220 into thePCB 222 when the sensor subassembly 202 is assembled. In someembodiments, the height of the contact bumps 320 is from about 0.1 toabout 1 mm. In some embodiments, the height of the contact bumps 320 isin the range from about 0.2 to about 0.3 mm. In one embodiment, thecontact bumps 320 have a height of about 0.26 mm. The height isgenerally selected to provide adequate force and pressure between thesensing element 220 and PCB 222.

In other embodiments, the contact bumps may have different shapes. Forexample, the bumps 320 may be generally circular, oval, square orotherwise shaped such that the bumps 320 are configured to press intocorresponding contact strips 223 on the PCB 222. The contact strips 223may be shaped differently as well. For example, the strips 223 may beshaped so as to generally correspond to the cross-sectional shape of thebumps 320. While there are two bumps 320 per contact strip 223 in theillustrated embodiment, other ratios of contact bumps 320 to contractstrips 223 are possible. For example, there may be one contact bump 320per contact strip 223, or more than two contact bumps 320 per contactstrip 223.

Referring again to FIGS. 2D-E, the frame 218 includes rounded edges 234around which the various components including the inner shield 226, thebonding layer 224, the sending element 220, and the outer shield 228wrap in the direction of the transverse axis 238. The rounded edges 234help assure that the sensing element 220 and other layers 226, 224, 228extend smoothly across the frame 3116, and do not include wrinkles,folds, crimps and/or unevenness. Rounded edges 234 advantageously allowuniform application of the sensing element 220 to the frame 218, whichhelps assure uniform, accurate performance of the sensor assembly 202.In addition, the dimensions of the rounded corners and the upper cavity230 can help to control the tension provided to the sensing element 220when it is stretched across the frame 218.

The frame 218 may have different shapes or configurations. For example,in some embodiments, the frame 218 does not include a recess 230 and thePCB 222 sits on top of the frame 218. In one embodiment the edges 234are not rounded. The frame 218 may be shaped as a board, for example.The frame 218 may include one or more holes. For example, the frame 218includes four elongate bars connected to form a hollow rectangle in oneconfiguration. In various embodiments, the frame 218 may not begenerally rectangular but may instead be generally shaped as a square,circle, oval or triangle, for example. The shape of the frame 218 may beselected so as to advantageously allow the sensor subassembly 202 to beapplied effectively to different areas of the body, for example. Theshape of the frame 218 may also be selected so as to conform to theshape of one or more of the other components of the sensor system 200such as the sensing element 220.

In addition, in some embodiments, one or more of the inner shield 226,the bonding layer 224, the sensing layer 220 and the outer shield 228are not wrapped around the frame 218. For example, in one embodiment,one or more of these components are generally coextensive with andattached to the underside of the frame 218 and do not include portionswhich wrap around the edges 234 of the frame.

Sensing Element

The sensing element 220 of certain embodiments is configured to senseacoustic vibrations from a measurement site of a medical patient. In oneembodiment, the sensing element 220 is a piezoelectric film, such asdescribed in U.S. Pat. No. 6,661,161, incorporated in its entirety byreference herein, and in the '883 Application. Referring still to FIGS.2D-E, the sensing element 220 includes upper portions 272 and lowerplanar portion 262. As will be discussed, in an assembled configuration,the top of the upper portions 272 include electrical contacts whichcontact electrical contacts on the PCB 222, thereby enablingtransmission of electrical signals from the sensing element 220 forprocessing by the sensor system. The sensing element 220 can be formedin a generally “C” shaped configuration such that it can wrap around andconform to the frame 218. Sensing elements in accordance withembodiments described herein can also be found in U.S. patentapplication Ser. No. 12/044,883, filed Mar. 7, 2008, which isincorporated in its entirety by reference herein. In some embodiments,the sensing element 220 includes one or more of crystals of tourmaline,quartz, topaz, cane sugar, and/or Rochelle salt (sodium potassiumtartrate tetrahydrate). In other embodiments, the sensing element 220includes quartz analogue crystals, such as berlinite (AlPO₄) or galliumorthophosphate (GaPO₄), or ceramics with perovskite or tungsten-bronzestructures (BaTiO₃, SrTiO₃, Pb(ZrTi)O₃, KNbO₃, LiNbO₃, LiTaO₃, BiFeO₃,Na_(x)WO₃, Ba₂NaNb₅O₅, Pb₂KNb₅O₁₅).

In other embodiments, the sensing element 220 is made from apolyvinylidene fluoride plastic film, which develops piezoelectricproperties by stretching the plastic while placed under a high poolingvoltage. Stretching causes the film to polarize and the molecularstructure of the plastic to align. For example, stretching the filmunder or within an electric field causes polarization of the material'smolecules into alignment with the field. A thin layer of conductivemetal, such as nickel-copper or silver is deposited on each side of thefilm as electrode coatings, forming electrical poles. The electrodecoating provides an electrical interface between the film and a circuit.

In operation, the piezoelectric material becomes temporarily polarizedwhen subjected to a mechanical stress, such as a vibration from anacoustic source. The direction and magnitude of the polarization dependupon the direction and magnitude of the mechanical stress with respectto the piezoelectric material. The piezoelectric material will produce avoltage and current, or will modify the magnitude of a current flowingthrough it, in response to a change in the mechanical stress applied toit. In one embodiment, the electrical charge generated by thepiezoelectric material is proportional to the change in mechanicalstress of the piezoelectric material.

Piezoelectric material generally includes first and second electrodecoatings applied to the two opposite faces of the material, creatingfirst and second electrical poles. The voltage and/or current throughthe piezoelectric material are measured across the first and secondelectrical poles. Therefore, stresses produced by acoustic waves in thepiezoelectric material will produce a corresponding electric signal.Detection of this electric signal is generally performed by electricallycoupling the first and second electrical poles to a detector circuit. Inone embodiment, a detector circuit is provided with the PCB 222, asdescribed in greater detail below.

By selecting the piezoelectric material's properties and geometries, asensor having a particular frequency response and sensitivity can beprovided. For example, the piezoelectric material's substrate andcoatings, which generally act as a dielectric between two poles, can beselected to have a particular stiffness, geometry, thickness, width,length, dielectric strength, and/or conductance. For example, in somecases stiffer materials, such as gold, are used as the electrode. Inother cases, less stiff materials, such as silver, are employed.Materials having different stiffness can be selectively used to providecontrol over sensor sensitivity and/or frequency response.

The piezoelectric material, or film, can be attached to, or wrappedaround, a support structure, such as the frame 218. As shown in FIGS.2D-E, the geometry of the piezoelectric material can be selected tomatch the geometry of the frame. Overall, the sensor can optimized topick up, or respond to, a particular desired sound frequency, and notother frequencies. The frequency of interest generally corresponds to aphysiological condition or event that the sensor is intended to detect,such as internal bodily sounds, including, cardiac sounds (e.g., heartbeats, valves opening and closing, fluid flow, fluid turbulence, etc.),respiratory sounds (e.g., breathing, inhalation, exhalation, wheezing,snoring, apnea events, coughing, choking, water in the lungs, etc.), orother bodily sounds (e.g., swallowing, digestive sounds, gas, musclecontraction, joint movement, bone and/or cartilage movement, muscletwitches, gastro-intestinal sounds, condition of bone and/or cartilage,etc.).

The surface area, geometry (e.g., shape), and thickness of thepiezoelectric material 220 generally defines a capacitance. Thecapacitance is selected to tune the sensor to the particular, desiredfrequency of interest. Furthermore, the frame 218 is structured toutilize a desired portion and surface area of the piezoelectricmaterial.

The capacitance of the sensor can generally be expressed by thefollowing relationship: C=εS/D, where C is the sensor's capacitance, εis the dielectric constant associated with the material type selected, Sis the surface area of the material, and D is the material thickness(e.g., the distance between the material's conducive layers). In oneembodiment, the piezoelectric material (having a predeterminedcapacitance) is coupled to an sensor impedance (or resistance) toeffectively create a high-pass filter having a predetermined high-passcutoff frequency. The high-pass cutoff frequency is generally thefrequency at which filtering occurs. For example, in one embodiment,only frequencies above the cutoff frequency (or above approximately thecutoff frequency) are transmitted.

The amount of charge stored in the conductive layers of thepiezoelectric material 220 is generally determined by the thickness ofits conductive portions. Therefore, controlling material thickness cancontrol stored charge. One way to control material thickness is to usenanotechnology or MEMS techniques to precisely control the deposition ofthe electrode layers. Charge control also leads to control of signalintensity and sensor sensitivity. In addition, as discussed above,mechanical dampening can also be provided by controlling the materialthickness to further control signal intensity and sensor sensitivity.

In addition, controlling the tension of the sensing element 220 in theregion where the mechanical stress (e.g., mechanical stress due toacoustic vibration from a patient's skin) is incident upon the sensingelement 220 can serve to improve the sensitivity of the sensing element220 and/or the coupling between the source of the signal (e.g., thepatient's skin) and the sensing element 220. This feature will bediscussed in greater detail below with respect to the coupler 214.

One embodiment of a piezoelectric sensing element 300 is provided inFIGS. 3A-C. The sensing element 300 includes a substrate 302 andcoatings 304, 306 on each of its two planar faces 308, 310. The planarfaces 308, 310 are substantially parallel to each other. At least onethrough hole 312 extends between the two planar faces 308, 310. In oneembodiment, the sensing element 400 includes two or three through holes312.

In one embodiment, a first coating 304 is applied to the first planarface 308, the substrate 302 wall of the through holes 312, and a firstconductive portion 314 of the second planar face 310, forming a firstelectrical pole. By applying a first coating 304 to the through holes312, a conductive path is created between the first planar face 308 andthe first conductive portion 314 of the sensing element 300. A secondcoating 306 is applied to a second conductive portion 316 of the secondplanar face 310 to form a second electrical pole. The first conductiveportion 314 and second conductive portion 316 are separated by a gap 318such that the first conductive portion 314 and second conductive portion316 are not in contact with each other. In one embodiment, the firstconductive portion 314 and second conductive portion 316 areelectrically isolated from one another.

In some embodiments, the first and second conductive portions 314, 316are sometimes referred to as masked portions, or coated portions. Theconductive portions 314, 316, can be either the portions exposed to, orblocked from, material deposited through a masking, or depositionprocess. However, in some embodiments, masks aren't used. Either screenprinting, or silk screening process techniques can be used to create thefirst and second conductive portions 314, 316.

In another embodiment, the first coating 304 is applied to the firstplanar face 308, an edge portion of the substrate 302, and a firstconductive portion 314. By applying the first coating 304 to an edgeportion of the substrate 302, through holes 312 can optionally beomitted.

In one embodiment, the first coating 304 and second coating 306 areconductive materials. For example, the coatings 304, 306 can includesilver, such as from a silver deposition process. By using a conductivematerial as a coating 304, 306, the multi-parameter sensor assembly canfunction as an electrode as well.

Electrodes are devices well known to those of skill in the art forsensing or detecting the electrical activity, such as the electricalactivity of the heart. Changes in heart tissue polarization result inchanging voltages across the heart muscle. The changing voltages createan electric field, which induces a corresponding voltage change in anelectrode positioned within the electric field. Electrodes are typicallyused with echo-cardiogram (EKG or ECG) machines, which provide agraphical image of the electrical activity of the heart based uponsignal received from electrodes affixed to a patient's skin.

Therefore, in one embodiment, the voltage difference across the firstplanar face 308 and second planar face 310 of the sensing element 400can indicate both a piezoelectric response of the sensing element 300,such as to physical aberration and strain induced onto the sensingelement 300 from acoustic energy released from within the body, as wellas an electrical response, such as to the electrical activity of theheart. Circuitry within the sensor assembly and/or within aphysiological monitor (not shown) coupled to the sensor assemblydistinguish and separate the two information streams. One such circuitrysystem is described in U.S. Provisional No. 60/893,853, filed Mar. 8,2007, titled, “Multi-parameter Physiological Monitor,” which isexpressly incorporated by reference herein.

Referring still to FIGS. 3A-C, the sensing element 300 is flexible andcan be wrapped at its edges, as shown in FIG. 3C. In one embodiment, thesensing element 400 is the sensing element 220 wrapped around the frame218, as shown in FIGS. 2D and 2E. In addition, by providing both a firstconductive portion 314 and a second conductive portion 316, both thefirst coating 304 and second coating 306 and therefore the firstelectrical pole of and the second electrical pole of the sensing element300 can be placed into direct electrical contact with the same surfaceof the PCB, such as the PCB 222 as shown FIGS. 5A-B below. Thisadvantageously provides symmetrical biasing of the sensing element 300under tension while avoiding uneven stress distribution through thesensing element 300.

Bonding Layer

Referring back to FIGS. 2D-E, the bonding layer 224 (sometimes referredto as an insulator layer) of certain embodiments is an elastomer and hasadhesive on both of its faces. In other embodiments, the bonding layer224 is a rubber, plastic, tape, such as a cloth tape, foam tape, oradhesive film, or other compressible material that has adhesive on bothits faces. For example, in one embodiment, the bonding layer 224 is aconformable polyethylene film that is double coated with a high tack,high peel acrylic adhesive. The bonding layer 224 in some embodiments isabout 2, 4, 6, 8 or 10 millimeters thick.

The bonding layer 224 advantageously forms a physical insulation layeror seal between the components of the sensor subassembly 202 preventingsubstances entering and/or traveling between certain portions of thesensor subassembly 202. In many embodiments, for example, the bondinglayer 224 forms a physical insulation layer that is water resistant orwater proof, thereby providing a water-proof or water-resistant seal.The water-resistant properties of the bonding layer 224 provides theadvantage of preventing moisture from entering the acoustic chamber orlower cavity 236. In certain embodiments, the sensing element 220, thebonding layer 224 and/or the shield layers 226, 228 (described below)form a water resistant or water proof seal. The seal can preventmoisture, such as perspiration, or other fluids, from entering portionsof the sensor subassembly 202, such as the cavity 236 when worn by apatient. This is particularly advantageous when the patient is wearingthe multi-parameter sensor assembly 200 during physical activity. Thewater-resistant seal prevents current flow and/or a conductive path fromforming from the first surface of the sensing element 220 to its secondsurface or vice versa as a result of patient perspiration or some othermoisture entering and/or contacting the sensing element 220 and/orsensor assembly 215.

The bonding layer 224 can also provide electrical insulation between thecomponents of the sensor subassembly 202, preventing the flow of currentbetween certain portions of the sensor subassembly 202. For example, thebonding layer 224 also prevents the inside electrical pole from shortingto the outside electrical pole by providing electrical insulation oracting as an electrical insulator between the components. For example,in the illustrated embodiment, the bonding layer 224 provides electricalinsulation between the sensing element 220 and the inner shield layer226, preventing the inside electrical pole of the sensing element 220from shorting to the outside electrical pole. In another embodiment, abonding layer is placed between the outer surface of the sensing element220 and the outer shield layer 228.

The elasticity or compressibility of the bonding layer 224 can act as aspring and provide some variability and control in the pressure andforce provided between the sensing element 220 and PCB 222. In someembodiments, the sensor assembly does not include a bonding layer 224.

Electrical Noise Shielding Barrier

An electrical noise shielding barrier can electrically shield thesensing element from external electrical noises. In some embodiments theelectrical shielding barrier can include one or more layers which form aFaraday cage around a piezoelectric sensing element, and whichdistribute external electrical noise substantially equally to theelectrical poles of the piezoelectric sensing element. In addition, theshielding barrier flexibly conforms to the surface shape of thepiezoelectric element as the surface shape of the piezoelectric elementchanges, thereby improving the shielding and sensor performance.

Referring still to FIGS. 2D-E, the electrical shielding barrier 227 ofthe illustrated embodiment includes first and second shield layers 226,228 (also referred to herein as inner and outer shield layers 226, 228)which form a Faraday cage (also referred to as a Faraday shield) whichencloses the sensing element 220 and acts to reduce the effect of noiseon the sensing element from sources such as external static electricalfields, electromagnetic fields, and the like. As will be described, oneor more of the inner and outer shield layers 226, 228 advantageouslyconform to the contours of the sensing element 220 during use, allowingfor enhanced shielding of the sensing element from external electricalnoise.

The inner and outer shield layers 226, 228 include conductive material.For example, the inner and outer shield layers 226, 228 includes copperin certain embodiments and are advantageously formed from a thin coppertape such that the layers can conform to the shape, contours andtopology of the sensor element 220 and the frame 218. In variousembodiments, one or more of the inner and outer shield layers 226, 228are from between about 0.5 micrometer and 10 micrometers thick. Forexample, the shield layers 226, 228, may be from between about 1.5 andabout 6 micrometers thick. In one embodiment, the inner and outer shieldlayers 226, 228 include copper tape about 3 micrometers thick. In yetother embodiments, the shield layers 226, 228 may be greater than 10micrometers thick or less than 0.5 micrometers thick. In general, thethickness of the shield layer 226, 228 is selected to provide improvedelectrical shielding while allowing for the shield layers 226, 228 toconform to the sensor element 220 and/or the frame 218. The inner shieldlayer 226 includes an adhesive on the inside surface 252 such that itcan adhere to the frame 218. The inner shield layer 226 adheres directlyto the frame 218 and advantageously conforms to the contours of theframe such as the rounded edges 234 and the lower cavity 236, adheringto the surface 250 defining the base of the cavity 236. The bondinglayer 224 (e.g., a tape adhesive) is wrapped around and generallyconforms to the contours of the inner shield layer 226 and the frame218. The sensing element 220 is wrapped around the bonding layer 224,the inner shield layer 224 and the frame 218. The outer shield layer 228is wrapped around and advantageously conforms to the contours of thesensing element 220 and the frame 218. In certain embodiments, a bondingor insulating layer is positioned between the sensing element 220 andthe outer shielding layer 228 as well. As such, the sensing element 220is sandwiched between and enclosed within the inner and outer shieldlayers 226, 228 which form a Faraday cage around the sensing element220. The configuration of the shield layers 226, 228, the sensingelement 220 and the bonding layer 224 will be described in greaterdetail below with respect to FIGS. 5A-B.

As discussed, the electrical shielding barrier 227 such as the Faradaycage formed by the inner and outer shield layers 226, 228 helps toreduce the effect of noise electrical noise on the sensing element 220from sources such as external static electrical fields andelectromagnetic fields, thereby lowering the noise floor, providingbetter noise immunity, or both. For example, the electrical shieldingbarrier 227 allows for the removal of electrical interference or noiseincident directed towards the sensing element 220 while allowing thenon-noise component of the sensed signal indicative of bodily sounds tobe captured by the sensor 215. For example, in one embodiment thesensing element 220 is a piezoelectric film such as one of thepiezoelectric films described herein having positive and negativeelectrical poles and configured in a differential mode of operation. Theelectrical shielding barrier 227 acts to balance the effect of the noiseby distributing the noise substantially equally to the positive andnegative electrical poles of the piezoelectric element. In someembodiments, the electrical shielding barrier 227 distributes the noiseequally to both the positive and negative poles. Moreover, the noisesignals distributed to the positive and negative electrical poles aresubstantially in phase or actually in phase with each other. Forexample, the noise signals distributed to the positive and negativepoles are substantially similar frequencies and/or amplitudes withsubstantially no phase shift between them.

Because the noise signal components on the positive and negative polesare substantially in phase, the difference between the noise componentson the respective poles is negligible or substantially negligible. Onthe other hand, the difference between the differential non-noise sensorsignal components indicative of bodily sounds on the positive andnegative poles will be non-zero because the sensing element isconfigured in a differential mode. As such, the noise signals canadvantageously be removed or substantially removed through a common-moderejection technique.

For example, a common-mode rejection element may receive a signalincluding the combined noise and non-noise sensor signal components ofthe positive and negative poles, respectively. The common-mode rejectionelement is configured to output a value indicative of the differencebetween the combined signal on the positive pole and the combined signalon the negative pole. Because the difference between the noise signalsis negligible, the output of the common-mode rejection element will besubstantially representative of the non-noise component of the sensorsignal and not include a significant noise component. The common moderejection element may include, for example, an operational amplifier. Inone embodiment, for example, three operational amplifiers (not shown)are used and they are disposed on the PCB 222.

Because the shielding layers 226, 228 conform to the topology of theframe 218 and the sensing element 220, the shielding layers 226, 228 arephysically closer to the electrical poles of the sensing element 220 andare more uniformly displaced from the sensing element 220. Moreover, theouter shield layer 228 of certain embodiments actively moves with andconforms to the contours of the sensing element 220 during use, such aswhen the sensor assembly is placed against the skin or when the sensingelement 220 is moving due to acoustic vibrations. For example, whenplaced against the skin, the coupling element 258 pushes against boththe outer shielding layer 228 of the shielding barrier 227 and thesensing element 220, causing them to curve along the inside surface ofthe coupling element 258 (FIG. 5A). Because the cage is flexible and canconform to the movement of the shielding element 220, the shieldingperformance and sensor performance is improved. This arrangementprovides advantages such as for example, for the noise signals to bemore accurately and evenly distributed to the positive and negativeelectrical poles of the sensing element 220 by the shielding layers 226,228, thereby providing enhanced noise reduction. This arrangement canalso provide for improved manufacturability and a more stream-lineddesign.

Alternative configurations for the electrical shielding barrier 227 arepossible. For example, the inner shield layer may not include anadhesive layer and may, for example, be held in place against the frame218 by pressure (e.g., from the locking posts 232). The outer shield 228may also include an adhesive layer in some embodiments. In various otherembodiments, the shield layers 226, 228 may include other materials suchas other types of metals. One or more of the shield layers may berelatively rigid in some configurations. In one embodiment, aninsulating layer or bonding layer is disposed between sensing element220 and the outer shield layer 228. In some embodiments, the innershield layer 226 actively conforms to the contours of the sensingelement 220 during use in addition to the outer shield layer 228. Inanother embodiment, the inner shield layer 226 actively conforms to thesensing element 220 during use and the outer shield layer 228 does not.In yet other embodiments, the sensor assembly 201 does not include anelectrical shielding barrier 227.

Acoustic Coupler

The sensor may also include an acoustic coupler or biasing element,which advantageously improves the coupling between the source of thesignal to be measured by the sensor (e.g., the patient's skin) and thesensing element. The acoustic coupler generally includes a couplingportion positioned to apply pressure to the sensing element so as tobias the sensing element in tension. For example, the acoustic couplermay include one or more bumps, posts or raised portions which providesuch tension. The bumps, posts or raised portions may be positioned onthe inner surface of the coupler, the outer surface of the coupler, orboth and may further act to evenly distribute pressure across thesensing element.

In certain embodiments, the acoustic coupler is configured to flex thesensing element, providing improved coupling. For example, the sensingelement is attached to the frame and generally stretched in tensionacross an open cavity of the frame, defining a plane. The acousticcoupler may then be attached to the frame such that it applies pressureto the sensing element, causing the sensing element to flex into thecavity and out of the plane. Such a configuration further biases thesensing element in tension and provides improved sensor operation.

In some embodiments, the acoustic coupler has a first side facing thesensing element and a second side facing the patient's skin whenattached to the patient. One or more of the first and second sides caninclude concave or convex surfaces, for example. In some embodiments,the acoustic coupler includes a concave portion on the second side and,and a convex portion on the first side. In certain embodiments, aportion on the second side of the coupler (e.g., a concaved portion,bump, post, raised portion, etc.) can be sized appropriately so as tocontact a patient's skin when the sensor is applied to the patient,providing improved sensor operation.

In addition, the acoustic coupler can be further configured to transmitbodily sound waves to the sensing element. The acoustic coupler can alsobe configured to provide electrical isolation between the patient andthe electrical components of the sensor. In certain embodiments, thesensing element is not electrically coupled to acoustic coupler, forexample.

In the illustrated embodiment, the acoustic coupler 214 houses the othercomponents of the sensor subassembly including the frame 218, the PCB222, the shield layers 226, 228, the bonding layers 224 and the sensingelement 220. The acoustic coupler 214 includes a non-conductive materialor dielectric. As shown, the acoustic coupler 214 generally forms adielectric barrier between the patient and the electrical components ofthe sensor assembly 201. As such, the acoustic coupler 214 provideselectrical isolation between the patient and the electrical componentsof the sensor subassembly 202. This is advantageous in avoidingpotential harmful electrical pathways or ground loops forming betweenthe patient and the sensor.

As shown in FIGS. 2D-E, the acoustic coupler 214 is formed in a hollowshell capable of housing the components of the other sensor subassembly202. Referring to FIG. 2D, the acoustic coupler 214 of the illustratedembodiment also includes recesses 256 and holes 252 capable of receivingand securing the button 212 (FIG. 2B) and portions of the elongatemember 210 (FIG. 2B) of the attachment subassembly 204.

FIG. 4 is a cross-sectional view of the acoustic coupler 214 taken alongthe line 5-5. In certain embodiments, the acoustic coupler includes abump or protrusion on the inner surface of the coupler 214 andconfigured to advantageously bias the sensing membrane in tension. Forexample, a coupling element 258 is disposed on the on the interiorbottom portion of the acoustic coupler 214 and which biases the sensingelement 220 in tension. The coupling element 258 of the illustratedembodiment is a generally rectangular bump which extends by a height habove the cavity 260 which is formed on the interior bottom of theacoustic coupler 214. The coupling element 258 is centered about andextends along the longitudinal axis 240 (FIGS. 2D and 2E) from near thefront of the acoustic coupler 214 to near the back of the acousticcoupler 214. In the illustrated embodiment, the coupling element 258 isabout ¼ of the width of the acoustic coupler 214 along the transverseaxis 238. As will be discussed in greater detail below with respect toFIG. 5A-B, the coupling element 258 can advantageously bias the sensingelement 220 in tension by applying pressure to the sensing element 220.Because the sensing element 220 may be generally taut in tension underthe pressure of the coupling bump 258, the sensing element 220 will bemechanically coupled to the coupling bump 258 and responsive to acousticvibrations travelling through the coupler 214 to the sensing element220, thereby providing improved coupling between the patient's skin andthe sensing element 220. As such, the acoustic coupler 214 provides forimproved measurement sensitivity, accuracy, or both, among otheradvantages.

The acoustic coupler 214 is further configured to transmit bodily soundwaves to the sensing element 220. The coupler 214 can further include aportion disposed on the outer surface of the coupler 214 and which isconfigured to contact the skin during use. For example, the acousticcoupler 214 can include an outer protrusion, bump or raised portion onthe outer surface. Referring to FIGS. 2E and 4, the underside of theacoustic coupler 214 includes portion 216 which is configured to contactthe skin of the patient and can provides contact between the skin andthe acoustic coupler 214. Acoustic vibrations from the skin will beincident on the portion 216, travel through the acoustic coupler to thecoupling bump 258 and eventually be incident on the sensing element 220held in tension by the bump 258. In addition, the contact portion 216may, in conjunction with the coupling element 258 or on its own, alsohelp to improve the coupling between the skin and the sensing element220. For example, when pressed against the skin, the contact portion 216may push a portion of the inner surface of the coupler 214, such as thecoupling element 258, into the sensing element 220, advantageouslyholding the sensing element 220 in tension. As shown, the contactportion 216 of the illustrated embodiment includes a semi-cylindricalbump mounted generally underneath the coupling element 258. Similar tothe coupling element 258, the contact portion 216 is centered about andextends along the longitudinal axis 240 from near the front of theacoustic coupler 214 to near the back of the acoustic coupler 214.Moreover, the acoustic coupler 214 acts to evenly distribute pressure tothe sensing element 220 during use. For example, because the couplingelement 258 and the portion 216 are generally positioned such that theyare centered with respect to surface of the sensing element 220,pressure will be distributed symmetrically and/or evenly across thesensing element 220.

Referring to FIG. 2E, a pair of slots 264 are disposed on either end ofthe contact portion 216 and each run generally along the transverse axisfrom near the left side of the acoustic coupler 214 to the right side ofthe acoustic coupler 214. The slots serve to decouple a segment 266 ofthe bottom of the acoustic coupler 214 including the coupling element258 and the contact portion 216 from the remainder of the acousticcoupler 214. As such, the segment 266 can move at least partiallyindependent from the rest of the acoustic coupler 214 in response toacoustic vibrations on the skin of the patient, thereby efficientlytransmitting acoustic vibrations to the sensing element 220. Theacoustic coupler 214 of certain embodiments includes an elastomer suchas, for example, rubber or plastic material.

In an alternative embodiment of the acoustic coupler 214, for example,the acoustic coupler 214 does not include a hollow shell and does nothouse the other components of the sensor subassembly. For example, thecoupler 214 may include a single planar portion such as, for example, aboard which couples to the underside of the frame 218 such that theshielding layers 226, 228, the sensing element 220 and the bonding layer224 are positioned between the coupler 214 and the frame 218. In someconfigurations, the coupler 214 is positioned between the frame 218 andone or more of the shielding layers 226, 228, the sensing element 220and the bonding layer 224. Moreover, the acoustic coupler 214 mayinclude a dielectric material, which advantageously electricallyisolates the electrical components of the sensor subassembly 202 fromthe patient. For example, the dielectric layer may ensure that there isno electrical connection or continuity between the sensor assembly andthe patient.

In certain embodiments, portions of the sensor assembly such as, forexample, the acoustic coupler 214 may include a gel or gel-likematerial. The gel may provide beneficial acoustic transmission, forexample, serving to enhance the coupling between the acoustic vibrationsfrom the patient's skin and the sensing element 220. The gel may provideacoustic impedance matching, for example, between the skin and thesensor. For example, the gel may serve to reduce the impedance mismatchfrom potential skin-to-air and air-to-sensing element discontinuity,thereby reducing potential reflections and signal loss. The gel may beembedded in a portion of the acoustic coupler 214. For example, one ormore of the coupling element 258 and the contact portion 216 may includea gel or gel-like material. The acoustic coupler 214 may include anembedded gel in certain embodiments where one or more of the couplingelement 258 and the contact portion 216 are not included. For example,the entire patient contact portion of the acoustic coupler 214 mayinclude gel material extending substantially from the patient contactsurface to the interior of the coupler 214 across the contact portion.One or more columns of gel material may extend from the patient contactsurface of the coupler 214 to the interior of the coupler 214 in otherembodiments. In yet further embodiments, the gel is not embedded in theacoustic coupler 214 but is added to the skin directly. In oneembodiment, the gel is embedded in the acoustic coupler 214 and isconfigured to be released from the coupler 214 when the sensor assemblyis applied to the patient. For example, gel can be filled in one or morecavities of the acoustic coupler 214 prior to use wherein the cavitiesare configured to open and release the gel when the coupler is pressedagainst the skin.

FIGS. 5A-B are cross-sectional views of the sensor subassembly 202 ofFIG. 2 along the lines 5A-5A and 5B-5B, respectively. As shown, theinner copper shield 226 is positioned as the inner most of the shieldlayers 226, 228, the bonding layer 224 and the sensing element 220.Referring to FIGS. 2D-E and FIGS. 5A-B, the four tabs 268 of the innercopper shield 226 are flat and extend across the top of the frame recess230 and the four corners of the top surface of the PCB (not shown inFIGS. 5A-B) which sits in the frame recess 230. The bonding layer 224 iswrapped around the inner copper shield 226. The upper portions 270 ofthe bonding layer 224 bend downward to conform to the shape of the frame218 such that they extend across and contact the bottom of the framecavity 230. The sensing element 220 is wrapped around the bonding layer224 and the upper portions 272 of the sensing element 220 also benddownward to conform to the shape of the frame 218. As such, the upperportions 272 of the sensing element 220 extend across the bottom of theframe cavity 230 and are in contact with the bottom of the PCB 222 andthe top surface of the bonding layer 224. The outer copper layer 228 iswrapped around the sensing element 220 and the upper planar portions 273of the outer copper shield 228 are flat, extend across the top of theframe recess 230, and are in contact with the top surface of the PCB(not shown).

The shield layers 226, 228, the bonding layer 224 and the sensingelement 220 wrap around the rounded edges 234 of the frame 218. Thelower planar portions 274, 276 of the inner shield layer 226 and thebonding layer 224 bend upwards so as extend across the bottom surface250 of the frame 218. The lower planar portions 262, 280 of the sensingelement 220 and the outer shield layer 228, on the other hand, extendbetween the lower frame cavity 236 and the coupler cavity 260. Moreover,the lower planar portions 262, 280 of the sensing element 220 and theouter shield layer 228 extend across the top of the coupling portion258. Because the coupler portion 258 extends slightly above the couplercavity 260 into the lower frame cavity 236 by the distance h, thesensing element 220 is advantageously biased in tension improving thesensitivity of the sensing element 220, the coupling of the sensingelement 220 to acoustic vibrations in the skin of the patient (notshown), or both.

In various embodiments, the components of the sensor subassembly 202 maybe arranged differently. For example, the components may be combinedsuch that the overall assembly include fewer discrete components,simplifying manufacturability. In one embodiment, one or more of theshielding layers 226, 228, the bonding layer 224 and the sensing element220 may include an integral portion (e.g., a multi-layered film). Insome embodiments, more than one bonding layer 224 is used. In oneembodiment, adhesive layers are formed on one or more of the shieldinglayers 226, 228 and the sensing element 220, and no separate bondinglayer 224 is present. In another embodiment, the various layers are heldtogether by pressure (e.g., from the contact posts 232 and/or PCB)instead of through the use of adhesives.

Referring still to FIGS. 2D-E and 5A-B, a method for attaching theshielding layers 226, 228, the bonding layer 224, the sensing element220 and the PCB 222 to the frame 218 includes providing the inner shield226 and attaching it to the frame 218. The sensing element 220 andbonding layer 224 are provided and also attached to the frame 218. Aprinted circuit board 222 is then provided. The printed circuit board222 is placed on top of the sensing element 220 such that a first edge280 of the printed circuit board 222 is placed over a first conductiveportion of the sensing element 220, and a second edge 282 of the printedcircuit board 222 is placed over a second conductive portion of thesensing element 220.

The printed circuit board 222 is pressed down into the sensing element220 in the direction of the frame 218. As the printed circuit board 222is pressed downward, the contact bumps (not shown) of the frame 218 pushthe bonding layer 224 and sensing element 220 into contact stripslocated along the first and second sides or edges 280, 282 of theprinted circuit board 222. The contact strips of the printed circuitboard 222 are made from conductive material, such as gold. Othermaterials having a good electro negativity matching characteristic tothe conductive portions of the sensing element 220, may be used instead.The elasticity or compressibility of the bonding layer 224 acts as aspring, and provides some variability and control in the pressure andforce provided between the sensing element 220 and printed circuit board222.

Once the outer shield 228 is provided and attached to the frame 218, adesired amount of force is applied between the PCB 222 and the frame 218and the locking posts 232 are vibrated or ultrasonically or heated untilthe material of the locking posts 232 flows over the PCB 222. Thelocking posts 232 can be welded using any of a variety of techniques,including heat staking, or placing ultrasonic welding horns in contactwith a surface of the locking posts 232, and applying ultrasonic energy.Once welded, the material of the locking posts 232 flows to amushroom-like shape, hardens, and provides a mechanical restraintagainst movement of the PCB 222 away from the frame 218 and sensingelement 220. By mechanically securing the PCB 222 with respect to thesensing element 220, the various components of the sensor sub-assembly202 are locked in place and do not move with respect to each other whenthe multi-parameter sensor assembly is placed into clinical use. Thisprevents the undesirable effect of inducing electrical noise from movingassembly components or inducing instable electrical contact resistancebetween the PCB 222 and the sensing element 220. In certain embodiments,the locking posts 232 provide these advantages substantially uniformlyacross multiple sensors.

Therefore, the PCB 222 can be electrically coupled to the sensingelement 220 without using additional mechanical devices, such as rivetsor crimps, conductive adhesives, such as conductive tapes or glues, likecyanoacrylate, or others. In addition, the mechanical weld of thelocking posts 232 helps assure a stable contact resistance between thePCB 222 and the sensing element 220 by holding the PCB 222 against thesensing element 220 with a constant pressure, for example, and/orpreventing movement between the PCB 222 and the sensing element 220 withrespect to each other.

The contact resistance between the sensing element 220 and PCB 222 canbe measured and tested by accessing test pads on the PCB 222. Forexample, in one embodiment, the PCB 222 includes three discontinuous,aligned test pads that overlap two contact portions between the PCB 222and sensing element 220. A drive current is applied, and the voltagedrop across the test pads is measured. For example, in one embodiment, adrive current of about 100 mA is provided. By measuring the voltage dropacross the test pads the contact resistance can be determined by usingOhm's law, namely, voltage drop (V) is equal to the current (I) througha resistor multiplied by the magnitude of the resistance (R), or V=IR.While one method for attaching the shield layers 226, 228, the bondinglayer 224, the sensing element and the PCB 222 to the frame 218 has beendescribed, other methods are possible. For example, as discussed, insome embodiments, one or more of the various separate layers arecombined in an integral layer which is attached to the frame 218 in onestep.

Printed Circuit Board

The PCB 222 includes various electronic components mounted to either orboth faces of the PCB 222. When sensor assembly is assembled and the PCB222 is disposed in the upper frame cavity 230, some of the electroniccomponents of the PCB 222 may extend above the upper frame cavity 230.To reduce space requirements and to prevent the electronic componentsfrom adversely affecting operation of the sensor assembly, theelectronic components can be low-profile, surface mounted devices. Theelectronic components are often connected to the PCB 222 usingconventional soldering techniques, for example the flip-chip solderingtechnique. Flip-chip soldering uses small solder bumps such ofpredictable depth to control the profile of the soldered electroniccomponents. The four tabs 268 of the inner copper shield 226 and theupper planar portions 273 of the outer copper shield 228 are soldered tothe PCB 222 in one embodiment, electrically coupling the electricalshielding barrier to the PCB 222.

In some embodiments, the electronic components include filters,amplifiers, etc. for pre-processing or processing a low amplitudeelectric signal received from the sensing element 220 (e.g., theoperational amplifiers discussed above with respect to the Faraday cage)prior to transmission through a cable to a physiological monitor. Inother embodiments, the electronic components include a processor orpre-processor to process electric signals. Such electronic componentsmay include, for example, analog-to-digital converters for convertingthe electric signal to a digital signal and a central processing unitfor analyzing the resulting digital signal.

In other embodiments, the PCB 222 includes a frequency modulationcircuit having an inductor, capacitor and oscillator, such as thatdisclosed in U.S. Pat. No. 6,661,161, which is incorporated by referenceherein. In another embodiment, the PCB 222 includes an FET transistorand a DC-DC converter or isolation transformer and phototransistor.Diodes and capacitors may also be provided. In yet another embodiment,the PCB 3114 includes a pulse width modulation circuit.

In one embodiment, the PCB 222 also includes a wireless transmitter,thereby eliminating mechanical connectors and cables. For example,optical transmission via at least one optic fiber or radio frequency(RF) transmission is implemented in other embodiments. In otherembodiments, the sensor assembly includes an information element whichcan determine compatibility between the sensor assembly and thephysiological monitor to which it is attached and provide otherfunctions, as described below.

Information Element

FIG. 6A is a top perspective view illustrating portions of anotherembodiment of a sensor system 600 including a sensor assembly 601suitable for use with any of the physiological monitors shown in FIGS.1A-C. The sensor assembly 601 includes a sensor 615, a cable assembly617 and a connector 605. The sensor 615, in one embodiment, includes asensor subassembly 602 and an attachment subassembly 604. The cableassembly 617 of one embodiment includes a cable 607 and a patient anchor603. The various components are connected to one another via the sensorcable 607. The sensor connector 605 can be removably attached to aphysiological monitor (not shown), such as through a monitor cable, orsome other mechanism. In one embodiment, the sensor assembly 601communicates with a physiological monitor via a wireless connection.

The sensor system 600 and certain components thereof may be generallysimilar in structure and function or identical to other sensor systemsdescribed herein, such as, for example, the sensor systems 100, 200described herein with respect to FIGS. 1-5.

For example, the sensor system 600 may include an electrical shieldingbarrier (FIGS. 6D-E) including one or more layers which form a Faradaycage around an piezoelectric sensing element (FIG. 6D-E), and whichdistribute external electrical noise substantially equally to electricalpoles of the piezoelectric sensing element. The shielding barrier orportions thereof of some embodiments can flexibly conform to the surfaceshape of the piezoelectric element as the surface shape of thepiezoelectric element changes, thereby improving the shielding andsensor performance.

The sensor system 600 may further include an acoustic coupler 614 whichcan including a bump positioned to apply pressure to the sensing elementso as to bias the sensing element in tension. The acoustic coupler canalso provide electrical isolation between the patient and the electricalcomponents of the sensor, beneficially preventing potentially harmfulelectrical pathways or ground loops from forming and affecting thepatient or the sensor.

The sensor system 609 may also include an attachment subassembly 604. Inone embodiment, the attachment subassembly 604 is configured to pressthe sensor against the patient's skin with a pre-determined amount offorce. The attachment subassembly 604 can be configured act in aspring-like manner to press the sensor 600 against the patient. Theattachment subassembly 604 can also be configured such that movement ofthe sensor 600 with respect to the attachment subassembly 604 does notcause the attachment subassembly 604 to peel off or otherwise detachfrom the patient during use.

Additionally, in some embodiments, a patient anchor 603 is providedwhich advantageously secures the sensor 615 to the patient at a pointbetween the ends of the cable 607. Securing the cable 607 to the patientcan decouple the sensor assembly 600 from cable 607 movement due tovarious movements such as accidental yanking or jerking on the cable607, movement of the patient, etc. Decoupling the sensor assembly 600from cable 607 movement can significantly improve performance byeliminating or reducing acoustical noise associated with cable 607movement. For example, by decoupling the sensor 600 from cable movement,cable movement will not register or otherwise be introduced as noise inthe acoustical signal generated by the sensor 600.

The shielding barrier, acoustic coupler 614, attachment subassembly 604,and patient anchor 603 may be generally similar in certain structuraland functional aspects to the shielding barrier, acoustic coupler 214,attachment subassembly 204, and patient anchor 203 of other sensorsystems described herein, such as the sensor system 200 described withrespect to FIGS. 2A-5B, for example.

FIGS. 6B-C are top and bottom perspective views of a sensor includingsubassembly 602 and an attachment subassembly 604 in accordance withanother embodiment of the present disclosure. The attachment subassembly604 generally includes lateral extensions symmetrically placed about thesensor subassembly 602. An embodiment of a similar attachmentsubassembly is described in detail with respect to FIG. 10.

FIG. 6D-E are top and bottom exploded, perspective views, respectively,of the sensor subassembly of FIGS. 6A-C. The frame 618 generallysupports the various components of the sensor such as the piezoelectricelement, electrical shielding barrier, attachment element and othercomponents. The sensor subassembly 602 includes an acoustic coupler 614,sensing element 620, adhesive layer 624, and first and second electricalshielding layers 626, 628 which may, in certain aspects, be generallysimilar in structure and function to the acoustic coupler 214, sensingelement 220, adhesive layer 224, and first and second electricalshielding layers 226, 228 of FIGS. 2A-2E, for example.

As shown, and unlike the embodiment shown in FIGS. 2A-E, the adhesivelayer 624 of FIG. 6D-E stretches straight across the frame 628 withoutconforming to the surface 650 on the underside of the frame 618. Thus,the sensing element 620 is sandwiched between the adhesive layer 624 andthe outer shielding layer 628. The adhesive layer 624 includes adhesiveover its entire outer surface which is in contact with the sensingelement 220. Moreover, the copper layer 628 may also include an adhesiveon its interior surface which contacts the other side of the sensingelement 220. As such, the adhesive layer 624 and the shielding layer 628bond to opposite sides of the sensing element 220, sandwiching andcreating a seal around it. This sandwiching and sealing of the sensingelement 620 improves the liquid resistivity of the sensor subassembly602 by impeding water or water vapors (e.g., from sweat or othersources) from ingressing and contacting the sensing element 220. Thus,the sandwiching of the sensing element 620 protects the sensor 602 fromundesired effects such as electrical shorting due to liquid ingress. Inone embodiment, the sensor 602 is IPX1 compliant.

The planar portion 625 of the adhesive layer 624, along with thecorresponding planar portions 621, 629 of the sensing element 620 andouter shielding layer 628, are configured to move with respect to thecavity defined by the underside of the frame 618 in response tovibrations. The adhesive layer 624 generally includes adhesive on all ofits surface area except for the interior surface of the planar portion625. As such, the adhesive layer 624 is securely bonded in place whilethe planar portion 625 can move freely with respect to the cavity duringoperation without sticking. Moreover, because the interior portion ofthe planar portion 625 is non-adhesive, foreign material such as dustparticles will generally not stick to the non-adhesive planar portion625, improving sensor operation.

Similar to the frame 218 of FIG. 2D, the frame 618 includes four lockingposts 632. However, the posts 632 of FIG. 6D are shown in a locked orliquefied configuration, unlike the posts 232 illustrated in FIG. 2D.

As shown in FIG. 6D, the shielding layers 626, 628 include flap portions668, 673 which conform to the frame 618 and sit underneath the PCB 222in an assembled configuration. Similarly, the sensing element 620 of thesensor subassembly 202 includes a flap portion 672 which conforms to theframe 618 and sits underneath the PCB 222. Upon welding of the lockingposts 232, the PCB 222 is pressed downwards into physical and electricalcontact with the flap portions 668, 673, 672 of the shielding layers626, 628 and sensing element 620. As such, because the flaps 668, 673,672 are configured to sit underneath the PCB 222, they are held in placein a pressure fit without soldering, improving manufacturability.

In addition, the sensor assembly can include any of a variety ofinformation elements, such as readable and/or writable memories.Information elements can be used to keep track of device usage,manufacturing information, duration of sensor usage, compatibilityinformation, calibration information, identification information, othersensor, physiological monitor, and/or patient statistics, etc. Theinformation element can communicate such information to a physiologicalmonitor. For example, in one embodiment, the information elementidentifies the manufacturer, lot number, expiration date, and/or othermanufacturing information. In another embodiment, the informationelement includes calibration information regarding the multi-parametersensor assembly 222. Information from the information element isprovided to the physiological monitor according to any communicationprotocol known to those of skill in the art. For example, in oneembodiment, information is communicated according to an I²C protocol.The information element may be provided on or be in electricalcommunication with the PCB 222 (see, e.g., 1500 b in FIG. 2D). Invarious embodiments, the information element can be located in anotherportion of the sensor assembly. For example, in one embodiment, theinformation element is provided on a cable connected to the PCB 222. Theinformation element may further be located on the sensor connector 205(see, e.g., 1500 a in FIG. 1B), the attachment subassembly 204, or someother part of the sensor assembly.

The information element can include one or more of a wide variety ofmemory devices known to an artisan from the disclosure herein, includingan EPROM, an EEPROM, a flash memory, a combination of the same or thelike. The information element can include a read-only device such as aROM, a read and write device such as a RAM, combinations of the same, orthe like. The remainder of the present disclosure will refer to suchcombination as simply EPROM for ease of disclosure; however, an artisanwill recognize from the disclosure herein that the information elementcan include the ROM, the RAM, single wire memories, combinations, or thelike.

The information element can advantageously store some or all of a widevariety data and information, including, for example, information on thetype or operation of the sensor, type of patient or body tissue, buyeror manufacturer information, sensor characteristics includingcalculation mode data, calibration data, software such as scripts,executable code, or the like, sensor electronic elements, sensor lifedata indicating whether some or all sensor components have expired andshould be replaced, encryption information, monitor or algorithm upgradeinstructions or data, or the like. In some embodiments, the informationelement can be used to provide a quality control function. For example,the information element may provide sensor identification information tothe system which the system uses to determine whether the sensor iscompatible with the system.

In an advantageous embodiment, the monitor reads the information elementon the sensor to determine one, some or all of a wide variety of dataand information, including, for example, information on the type oroperation of the sensor, a type of patient, type or identification ofsensor buyer, sensor manufacturer information, sensor characteristicsincluding history of the sensor temperature, the parameters it isintended to measure, calibration data, software such as scripts,executable code, or the like, sensor electronic elements, whether it isa disposable, reusable, or multi-site partially reusable, partiallydisposable sensor, whether it is an adhesive or non-adhesive sensor,sensor life data indicating whether some or all sensor components haveexpired and should be replaced, encryption information, keys, indexes tokeys or has functions, or the like monitor or algorithm upgradeinstructions or data, some or all of parameter equations, informationabout the patient, age, sex, medications, and other information that canbe useful for the accuracy or alarm settings and sensitivities, trendhistory, alarm history, sensor life, or the like.

FIG. 7 shows one embodiment of a information element 700. Informationelement 700 has a read only section 702 and a read write section 704.The read only and read write sections can be on the same memory or on aseparate physical memory. In addition, the read only block 702 and theread write block 704 can include multiple separate physical informationelements or a single information element. The read only section 702contains read only information, such as, for example, sensor lifemonitoring functions (SLM) 706, near expiration percentage 708, updateperiod 710, expiration limit 712, index of functions 714, sensor type orthe like. For example, in some embodiments, the index of functions 714includes configuration information related to what parameters can bemeasured by the sensor (e.g., ventilation, apnea, respiration rate,etc.). In one embodiment, the information element 700 providesinformation related to the sensitivity of the sensing element,information related to the mechanical configuration of the sensor, orsome other type of configuration or calibration information.

The read write section 704 contains numerous read write parameters, suchas the number of times sensor is connected to a monitoring system 716,the number of times the sensor has been successfully calibrated 718, thetotal elapsed time connected to monitor system 720, the total time usedto process patient vital parameters 722, the cumulative temperature ofsensor on patient 724, the expiration status 726. Although described inrelation to certain parameters and information, a person of ordinaryskill in the art will understand from the disclosure herein that more orfewer read only and read/write parameters can be stored on the memory asis advantageous in determining the useful life of a sensor or some otherparameter.

FIG. 8 illustrates a flow chart of one embodiment of the read/writeprocess between the monitor and the sensor. In block 802, the monitorobtains sensor parameters from the sensor. For example, in block 802,the monitor can access the read only section 702 of the informationelement in order to obtain functions such as SLM functions 706, nearexpiration percentage 708, update period 710, expiration limit 712,and/or the index of functions 714 (FIG. 7). The monitor uses thesefunctions in block 804 to track sensor use information. In block 804,the monitor tracks sensor use information, such as, for example, theamount of time the sensor is in use, the amount of time the sensor isconnected, the average temperature, as well as any other stress that canbe experienced by the sensor. The monitor then writes this useinformation on a periodic basis to the sensor at block 806. At decisionblock 808, the monitor decides whether or not the sensor life is expiredbased on the obtained parameters from the sensor and the useinformation. If the sensor's life has not expired at block 808, then thesystem returns to block 804 where the monitor continues to track sensoruse information. If, however, at decision block 808 the monitor decidesthat the sensor life has expired, the monitor will display a sensor lifeexpired at block 810.

Sensor use information can be determined in any number of ways. Forexample, in an embodiment, the time period in which power is provided tothe sensor is determined and an indication stored in memory. In anembodiment, the amount of current supplied to the sensor is monitoredand an indication is stored in memory. In an embodiment, the number oftimes the sensor is powered up or powered down is monitored and anindication is stored in memory. In an embodiment, the number of timesthe sensor is connected to a monitor is tracked and an indication isstored in memory. In an embodiment, the number of times the sensor isplaced on or removed from a patient is monitored and an indication isstored in the memory. The number of times the sensor is placed on orremoved from a patient can be monitored by monitoring the number ofprobe off conditions sensed, or it can be monitored by placing aseparate monitoring device on the sensor to determine when the sensor orportions thereof are sensor depressed, opened, removed, replaced,attached, etc.

In an embodiment, the average operating temperature of the sensor ismonitored and an indication stored. This can be done, for example,through the use of bulk mass as described above, or through directlymonitoring the temperature of the sensing element, or the temperature ofother parts of the sensor. In an embodiment, the number of differentmonitors connected to the sensor is tracked and an indication is storedin memory. In an embodiment, the number of times the sensor iscalibrated is monitored, and an indication is stored in the memory. Inan embodiment, the number of patients which use a sensor is monitoredand an indication is stored. This can be done by, for example, bystoring sensed or manually entered information about the patient andcomparing the information to new information obtained when the sensor ispowered up, disconnected and/or reconnected, or at other significantevents or periodically to determine if the sensor is connected to thesame patient or a new patient.

In an embodiment, a user is requested to enter information about thepatient that is then stored in memory and used to determine the usefulsensor life. In an embodiment, a user is requested to enter informationabout cleaning and sterilization of the sensor, and an indication isstored in the memory. Although described with respect to measuringcertain parameters in certain ways, a person of ordinary skill in theart will understand from the disclosure herein that various electricalor mechanical measurement can be used to determine any useful parameterin measuring the useful life of a sensor.

The monitor and/or the sensor determines the sensor life based on sensoruse information. In an embodiment, the monitor and/or sensor uses aformula supplied by the sensor memory to measure the sensor life usingthe above described variables. In an embodiment, the formula is storedas a function or series of functions, such as SLM functions 706. In anembodiment, experimental or empirical data is used to determine theformula used to determine the sensor's life. In an embodiment, damagedand/or used sensors are examined and use information is obtained inorder to develop formulas useful in predicting the useful sensor life.

In an embodiment, a formula or a set of formulas is stored in themonitor's memory. An indication of the correct formula or set offormulas to be used by the monitor is stored in the sensor. Theindication stored on the sensor is read by the monitor so that themonitor knows which formula or series of formulas are to be used inorder to determine the useful life of the sensor. In this way, memoryspace is saved by storing the functions or set of functions on themonitor's memory and only storing an indication of the correct functionor functions to be used on the sensor memory. Further details regardingembodiments of sensor information elements and systems and methods formonitoring sensor life can be found in U.S. Publication No.2008/0088467, which is hereby incorporated in its entirety by referenceherein.

Attachment Subassembly

The acoustic sensor can also include an attachment subassemblyconfigured to press the sensor against the patient's skin with apre-determined amount of force. The attachment subassembly can includelateral extensions symmetrically placed about the sensor such aswing-like extensions or arms that extend from the sensor. In otherembodiments, the attachment subassembly has a circular or rounded shape,which advantageously allows uniform adhesion of the attachmentsubassembly to an acoustic measurement site. The attachment subassemblycan include plastic, metal or any resilient material, including a springor other material biased to retain its shape when bent so as to act in aspring-like manner to advantageously press the sensor against thepatient. Moreover, the attachment subassembly can also include anattachment layer which may interact with the elongate member so as toadhesively attach to the patient without peeling off of the patient.

FIG. 9A is a perspective, exploded view of an attachment subassembly 904according to an embodiment of the disclosure. The attachment subassembly904 may be the attachment subassembly 204 of FIG. 2. The attachmentsubassembly 904 couples a sensor, such as the sensor subassembly 202, tothe skin of the patient. The attachment subassembly 904 includes firstand second elongate portions 906, 908 each comprising top tape portions914, bottom tape portions 916 and liner portions 918. The attachmentsubassembly 904 further includes a button portion 912 which mechanicallymates the attachment subassembly 904 to the sensor subassembly. Theattachment subassembly 904 is sometimes referred to as an attachmentelement or spring assembly.

A elongate member 910 includes a strip of resilient material in certainembodiments. For example, the elongate member 910 includes a resilient,bendable material which rebounds readily after being bent, issemi-rigid, acts as a spring or is elastic or semi-elastic. The elongatemember 910 of the illustrated embodiment is sandwiched between the topand bottom tape portions 914, 916 when the attachment subassembly 904 isassembled. The elongate member 910 includes first and second tonguesegments 930, 932 which form part of the first and second elongateportions 906, 908, respectively. The elongate member 910 may be referredto as or may include a spring portion. For example, the tongue segments930, 932 may be described as a spring portion of the elongate member910. The entire elongate member 910 may be referred to as a springportion in other embodiments. The elongate member 910 further includes agenerally circular center portion 928. The circular portion 928 includesone or more holes 924, 926 for receiving one or more mating features 928on the button 912. The elongate member 910 includes plastic in oneembodiment.

For each of the first and second elongate portions 906, 908, theunderside of the top tape portion 914 includes an adhesive substancewhich adheres to the top of the bottom tape portion 916 and to the topof the tongue segments 930, 932 of the elongate member 910 in anassembled configuration. In addition, the underside of the bottom tapeportion 916 includes an adhesive substance which is revealed when theliner portion 918 is removed from the bottom tape portion 916. Forexample, the user can remove the liner portion 918 by pulling on the tabportion 920. The bottom tape portion 916 of each of the first and secondelongate portions 906, 908 can then be attached to the skin of thepatient. The portion of the elongate portions 906, 908 which attach tothe patient are sometimes referred to as attachment portions 917. Insome embodiments, the attachment portions are positioned on otherportions of the attachment subassembly 904 rather than on the bottomtape portion 916, such as, for example, directly on the elongate member910.

FIG. 9B is a side view of the attachment subassembly 904 attached to asensor subassembly 902. The sensor subassembly 902 may be the sensorsubassembly 202 of FIG. 2 or some other sensor subassembly. Theattachment subassembly 904 advantageously improves the connectionbetween the patient's skin and the sensor subassembly 902, providingbetter sensor performance and more efficient use. The elongate member910 includes a resilient material which allows the first and secondtongue segments 930, 932 and the corresponding first and second elongateportions 906, 908 to be bent from a first, unattached position in thedirection y such that the first and second elongate portions 906, 908can be adhesively attached to the patient's skin at a second, attachedposition. While the elongate member 910 is positioned generally on thetop of the sensor subassembly 902 in the illustrated embodiment, otherconfigurations are possible. For example, in some embodiments, theelongate member extends from a middle portion of the sensor subassembly954 such as from a middle portion of the support frame. In oneembodiment, for example, the elongate member 910 includes two or moreseparate pieces which attach to and extend from opposing sides of thesensor subassembly 954. In another embodiment, the elongate member 910includes one integral piece which extends through the body of the sensorsubassembly 954 and includes two or more arms which extend from opposingsides of the sensor sub assembly 954.

In the bent, attached, configuration, the elongate member 910 is intension. As such, the center portion 928 of the elongate member 910urges downward, towards the skin of the patient in the direction y inorder to achieve equilibrium with the tongue segments 930, 932. Thecenter portion 928 will therefore exert a predetermined force in the ydirection on the top of the sensor subassembly 902, advantageouslybiasing the contact portion 916 of the acoustic coupler 914 against thepatient's skin. The elongate member 910 thereby provides an improvedcontact between the skin and the sensor subassembly 902. For example,the elongate member 910 provides greater pressure and/or more uniformpressure between the skin and the sensor subassembly 902 in certainembodiments. The improved coupling also advantageously enhances thereliability of sensor measurements. Moreover, because the spring-likecharacteristics of the spring portion of the elongate member 910 mayvary based on the stiffness of the spring portion, the predeterminedforce with which the sensor subassembly 902 is pressed against the skinmay be determined at least in part based on a stiffness of the springportion. In addition, the because the elongate member 910 will generallyremain in tension while sensor is attached to the patient, theattachment subassembly 904 will generally apply a continuous force onthe sensor subassembly 954.

The attachment subassembly 904 is further configured to advantageouslyallow for a continued secure connection between the sensor subassemblyand the patient in the event of stretching of the patient's skin.Because the elongate member is in tension when in the bent, attached,configuration, the tongue segments 930, 932 will urge the attachmentportions 917 at least partially laterally, away from the sensorsubassembly 902. As such, the patient's skin may stretch laterally, awayfrom the sensor subassembly 902. However, as the skin stretches, theelongate member 910 is configured such that the center portion 928 willapply an increased force on the sensor subassembly 902. The amount ofincreased force may correspond to the amount of stretching, for example.As such, the attachment subassembly 904 is configured to apply acontinuous force on the sensor subassembly 904, such as to the frame ofthe sensor subassembly 904, thereby pressing it into the patient's skinas the medical patient's skin stretches.

The attachment subassembly 904 may be provided in a variety ofalternative configurations as well. For example, the elongate member 910may bend away from the frame 218 when the sensor assembly 201 is notattached to the patient. In one embodiment the elongate member 910 isformed in a pre-biased configuration so as to increase the amount ofpressure the attachment subassembly 904 exerts on the connection betweenthe sensor subassembly 902 and the skin. For example, in one embodiment,the elongate member 910 is not flat but is instead formed in a curvedconfiguration such that the tongue segments 930, 932 are bent upwards,away from the skin prior to adhesion of the sensor subassembly 902 tothe skin. Accordingly, when the tongue segments 930, 932 and theelongate portions 906, 908 are bent downwards to attach the sensor tothe patient, greater pressure is exerted by the center portion 928 ofthe elongate member 910 on the sensor subassembly 902 due to the biasthat is built into the elongate member 910. In other embodiments,different materials or components may be used or combined. For example,in one embodiment, the elongate member includes a metal material.

In some embodiments, the attachment subassembly 904 itself is used tomeasure one or more sensor to skin coupling parameters. For example, inone embodiment the attachment subassembly 904 includes an auxiliarysensor (not shown) which can provide an output signal indicative of theactual force being applied by the sensor subassembly 902 on the skin.The elongate member 910, for example, may include a strain gauge whichcan measure the strain of the elongate member 910. The strainmeasurement may then be used, for example, to determine the force beingapplied by the sensor subassembly on the skin. In one embodiment, thestrain gauge includes a Wheatstone bridge circuit. In certainembodiments, the signals from the auxiliary sensor may be communicatedto electronics on the sensor assembly for further processing, such as toone of the processors and/or information elements described herein. Inother embodiments, separate electrical leads may be used to communicatethe signals from the pressure sensor to the patient monitor.

Measurements from the auxiliary sensor may be used for a variety ofpurposes. Measurements from an auxiliary sensor such as the strain gaugemay be used, for example, to determine whether the sensor subassembly902 is coming loose from the skin or otherwise not in sufficientconnection with the skin to produce a reliable measurement. For example,since the skin is elastic, it may stretch over time, particularly whenattached to a sensor 201. Therefore, providing a strain gauge or otherpressure, strain or tension, etc., measuring device with the backbone910 allows the physiological monitoring system 100 to intelligentlymonitor the quality of the sensor-to-skin coupling, and adapt to changesin the coupling condition. In this way, the monitor 100 may provide anoutput signal based on a measured physiological signal, such as anacoustic sound coming from within the patient, and a coupling signal,indicating the quality of the sensor-to-skin coupling. The couplingsignal may include a strain, pressure, tension or other signalindicative of the sensor-to-skin coupling.

The system may indicate an alarm condition and/or may automaticallyshut-down operation of the sensor in the event of a poor connection, forexample. In such embodiments the attachment subassembly 904 triggers analarm. The auxiliary sensor readings may also be used to calibrate thesensor. For example, if the auxiliary sensor indicates that theconnection between the sensor subassembly 902 and the skin is relativelyweak, the system may increase the sensitivity of the sensor or increasethe gain of an amplifier configured to amplify the sensor signal. On theother hand, if the auxiliary sensor indicates that the connectionbetween the sensor subassembly 902 and the skin is relatively strong,the system may decrease the sensitivity of the sensor or decrease thegain of an amplifier configured to amplify the sensor signal. In someembodiments, the user may optionally change the calibration of thesensor based on the auxiliary readings and the system does notautomatically change the calibration.

The auxiliary sensor reading may be used to evaluate physiologicalmeasurement signals from the sensor (e.g., measurements relating toventilation, apnea, respiration rate and the like). For example, ifthere is a change in a physiological measurement, the system mayevaluate the auxiliary sensor reading to determine whether the change inthe physiological measurement was actually at least in part due to afaulty connection between the sensor and the patient. In anotherembodiment, the auxiliary sensor may be connected to a portion of thesensor subassembly 902. For example, in one embodiment, the contactportion 916 of the acoustic coupler 914 includes a pressure sensor whichmeasures the force being applied to the skin.

Various embodiments of auxiliary sensors and auxiliary sensorconfigurations may be provided. For example, an auxiliary sensor may beincluded on other parts of the sensor assembly instead of, or inaddition to, the attachment subassembly. For example, the sensorsubassembly includes an auxiliary sensor in one embodiment. In variousembodiments, the auxiliary sensor may be a push-button or scale typepressure sensor, a temperature sensor or the like.

As discussed above, in certain embodiments the sensor is resposable andhas both disposable and reusable parts. For example, in one embodimentthe attachment subassembly 904 or portions thereof are disposable and/orremovably attachable from the sensor subassembly 902. The attachmentsubassembly 904 can removably attach to the sensor subassembly via asnap-fit mechanism. The attachment subassembly 904 may removably attachto the sensor subassembly 902 via other mechanisms such as, for example,friction-fit mechanisms, adhesive mechanisms and the like. In variousother embodiments, the disposable element, such as the attachmentsubassembly 904, may attach via one of the attachment mechanismsdescribed in the '345 patent, such as an attachment mechanism similar toone of those described with respect to column 5, line 15 through column8, line 26, for example. A removably attachable and/or disposableattachment subassembly 904 can be advantageous for several reasons. Forexample, the attachment subassembly 904 or components thereof (e.g., theadhesive portions) may wear out relatively quickly in comparison to theother components of the sensor assembly (e.g., in comparison to thesensor subassembly 902) or may become soiled due to direct adhesivecontact with the skin. Moreover, the attachment subassembly 904 may berelatively less costly to manufacture than the other components of thesensor assembly. As such, in the event that attachment subassembly 904becomes damaged, a removably attachable and/or disposable attachmentsubassembly 904 can reduce costs because a user will not have to replacethe entire sensor assembly. In addition, in the event that theattachment subassembly 904 becomes soiled, the user can optionallyreplace only the attachment subassembly 904 rather than take the time tosterilize it for subsequent use.

The attachment subassembly 904 may further include an informationelement (not shown) which can provide information to the system. Theinformation element may be one of the information elements describedherein or may be another information element. For example, theinformation element may monitor the life of the sensor assembly, theattachment subassembly 904 or another part of the sensor assembly in themanner described above with respect to FIGS. 7 and 8. In one embodiment,the information element may store the information provided by anauxiliary sensor on the attachment subassembly 904, such as, forexample, the strain gauge described above. The information element mayprovide information to the system which can be used to configure thesensor. In some embodiments, the information element can be used toprovide a quality control function. For example, the information elementmay provide identification information to the system which the systemuses to determine whether the attachment subassembly 904 is compatiblewith the system. In another embodiment, the information element providesuse information related to the amount of use of the attachmentsubassembly 904.

As mentioned above, the attachment subassembly can also include anattachment layer which may interact with the elongate member so as toadhesively attach to the patient without peeling off of the patient. Theattachment subassembly may include an elongate member that includes aresilient material and is coupled to the attachment layer. Theattachment layer may include one or more of the bottom tape portions 916and the top tape portions 914 of FIGS. 9A-9B, for example. For example,the elongate member can be configured to move from a first position inwhich the elongate member is substantially parallel to the attachmentlayer to a second position in which the elongate member is inclined atan angle with respect to the attachment layer when the attachment layeris attached to the medical patient.

FIGS. 9C-D show an embodiment of an attachment subassembly 950 attachedto the patient's skin 951 and in an unattached configuration,respectively. The attachment subassembly 950 includes an attachmentelement 952 supported by the sensor subassembly 954 and extending beyonda first side 956 of the sensor subassembly 954.

The attachment element 952 includes an attachment layer 958 having apatient attachment surface 960. As shown, an end 975 of the elongatemember 974 is positioned a predetermined distance from an edge 976 ofthe attachment layer 958. A connecting portion 966 of the attachmentelement 952 is attached to the top of the elongate member 974, couplingthe elongate member 974 to the attachment layer 958. As shown in FIG.9C, the elongate member 974 is positionable in a first position in whichthe elongate member 974 is substantially parallel or parallel to theattachment layer 958. The elongate member 974 is positioned in the firstposition, for example, when the attachment surface 960 of the attachmentlayer 958 is not attached to the skin 951 of the patient. Moreover, asshown in FIG. 9D, the elongate member 974 is configured to move to asecond position from the first position in which the elongate member 974is inclined at an angle θ with respect to the attachment layer when theattachment surface 960 is attached to the skin 951 of the patient.

When in the attached, bent configuration of FIG. 9D, the elongate member974 will urge upward. As such, the elongate member 974 will urge theconnecting portion 966 and thus the attachment layer 958 upward as well.Moreover, movement of the sensor subassembly 954 due to acousticvibrations or movement of the patient, for example, will urge theelongate member 974 and thus the attachment layer 958 away from the skinof the patient. However, the elongate member 974 is connected to theattachment layer such that neither the movement of the sensorsubassembly 954 with respect to the attachment layer nor the force fromthe elongate member 974 cause the attachment layer to detach from themedical patient during use.

As shown in FIG. 9D, in the bent, attached configuration, the elongatemember 974 and the attachment layer 958 are not adhesively or otherwiseconnected in the region 978 formed between the top of the attachmentlayer 958 and the underside of the elongate member 974, advantageouslyallowing for the elongate member 974 to incline with respect to theattachment layer 958. In addition, the elongate member 974 is positionedat a distance from the edge 976 of the attachment layer 958 and theforce incident on the attachment layer 958 in the upward direction fromthe elongate member 974 is therefore distributed near the end 975 of theelongate portion 974 rather than at the edge 976. As such, the force isdistributed away from the edge 976 of the connection of the attachmentlayer 958 and the skin. Upward force away from the edge of attachmentlayer 958 has less of a tendency to peel the attachment layer 958 off ofthe skin, thus reducing unintended detachments and thereby providing forimproved and more reliable measurement.

The distance that the end 975 of the elongate member 974 and ispositioned from the edge 976 of the attachment layer 958 is selected soas to reduce the tendency of peel off. For example, the end 975 of theelongate member 974 may be positioned near the attachment layer's 958center in certain embodiments. In addition, the angle θ may be afunction of various factors such as, for example, the stiffness of theelongate member 974. The angle θ may also be a function of the distancethe end 975 of the elongate member travels to the skin from the firstposition to the second position. This distance may correspond, in oneembodiment, to approximately height of the sensor subassembly 954 wherethe elongate member 974 is positioned on the top of the sensorsubassembly 954, for example. In some alternative embodiments, however,the connecting portion couples to the attachment layer 958 substantiallynear or at the edge 976 of the attachment layer 958.

As shown, the attachment subassembly 950 further includes a secondattachment element 972 extending from a second side 970 of the sensorsubassembly 954 substantially opposite the first side 956. In someembodiments, more than two attachment elements can be included. Forexample, in one embodiment, a third and fourth attachment element extendbeyond opposing third and fourth sides of the sensor subassembly 954. Inone embodiment, only one attachment element is included. In someembodiments, the connecting portion 966 may include a tape portion suchas the top tape portion 914 described above.

The connecting portion 966 may further include an elongate member 974comprising a resilient material. The elongate member may be, forexample, the elongate member 910 described above or some other elongatemember or spring. The elongate member 974 may be coupled to the sensorsubassembly 954 but not be substantially coupled to the attachment layer958. Like the elongate member 910, the elongate member 974 may beconfigured to apply a predetermined force on the frame such that thesensor subassembly is pressed against a measurement site of the medicalpatient during use.

Referring back to the attachment subassembly 904 of FIGS. 9A-B, thebottom surface of the bottom tape portion 916 includes an adhesive whichattaches to the patient's skin. Moreover, the underside of the top tapeportion 914 includes an adhesive and attaches to the top of the elongatemember 910 and to the top of the bottom tape portion 916. As such, thetop tape portion 914 couples the elongate member 910 to the bottom tapeportion 918. Accordingly, the top tape portion acts as a the connectingportion, such as the connecting portion 966 described above, and thebottom tape portion 916 acts as the attachment layer 958, as describedabove.

Moreover, the top surface of the bottom tape portion (attachment layer)916 is not adhesive and thus does not adhere to the bottom of theelongate member 910. As such, the top tape portion 914 and the elongatemember 910 the elongate member 910 is positionable in a first positionin which the elongate member 910 is substantially parallel or parallelto the bottom tape portion 918 and is configured to move to a secondposition from the first position in which the elongate member 910 isinclined at an angle θ with respect to the bottom tape portion 918 orattachment layer when the attachment surface 960 is attached to the skin951 of the patient. As such, and as described above with respect toFIGS. 9C-D, the upward force from the elongate member 910 in the bent,attached configuration will be distributed away from the edge 976 of theconnection of the bottom tape portion 918 and the skin, thereby reducingthe incidence of peel off or other unintended detachment of the sensor.

Referring again to FIGS. 9C-D, the connecting portion 966 and theattachment layer 958 may form an integral piece. In other embodiments,as discussed above, the connecting portion 966 and the attachment layer958 include separable units, such as bottom and top layers of tape, forexample. In certain embodiments where the connecting portion 966includes adhesive, only select portions of the bottom surface of theconnecting portion 966 include such adhesive. For example, in oneembodiment, only the portion of the connecting portion 966 whichcontacts the elongate member 974 includes an adhesive. In anotherembodiment, only a select portion of the connecting portion 966 whichadhesively attaches to the attachment layer 958 includes adhesive. Inyet other configurations, the connecting portion includes adhesive whichconnects to both the elongate member 974 and to a select portion whichattaches to the attachment layer 958.

FIG. 10 is a perspective, exploded view of an attachment subassembly1004 compatible with any of the sensor assemblies of FIGS. 1A-2E and6A-E according to another embodiment of the disclosure. The attachmentsubassembly 1004 may be the attachment subassembly 604 of FIG. 6, forexample. Similar to other attachment elements described herein, theattachment subassembly 1004 couples a sensor, such as the sensorsubassembly 602, to the skin of the patient and can be configured topress the sensor against the patient's skin with a pre-determined amountof force, acting in a spring-like manner to press the sensor against themeasurement site. The attachment subassembly 1004 can also be configuredsuch that movement of the sensor with respect to the attachmentsubassembly 1004 does not cause the attachment element to peel off orotherwise detach from the patient during use. For example, theattachment subassembly 1004 may operate in a similar manner and providesimilar advantages and functions to other attachment elements described(e.g., the attachment subassembly 900 described with respect to FIGS.9A-9D).

The attachment subassembly 1004 has a first end 1006 and a second end1008. The attachment subassembly 1004 includes a top tape portion 1014,bottom tape portions 1016, liner portion 1018, and an elongate member1010. The attachment subassembly 1004 further includes a button 1012which mechanically mates the attachment subassembly 1004 to the sensorsubassembly (not shown). In one embodiment, the top tape portion 1014 istranslucent and includes adhesive on its underside. The top tape portionadheres to the top of the elongate member 1010 and the top of the upperbottom tape portion 1016. The upper bottom tape portion 1016 includesprinted text that is visible through the translucent top tape portion1016. The underside of the upper bottom tape portion 1016 adheres to thetop of the lower bottom tape portion 1016. The liner 1018 protects thebottom tape portion and can be peeled off to expose adhesive on theunderside of the lower bottom tape portion 1016.

The attachment subassembly 1004 is sometimes referred to as anattachment element or spring assembly. The elongate member 1010 of FIG.10 can include any of variety of shapes, including a forked or “Y”shape, and the elongate member 1010 includes a first end 1020 having oneleg 1022 and a second end 1024 having two legs 1026.

The forked structure provides certain advantages. For example, themultiple-legged structure of the second end 1024 may provide anincreased amount of spring action in pressing the sensor against theskin, or may provide a more evenly distributed and/or efficientlydirected force.

The single-legged structure of the first end 1020 allows for enhancedadhesion to the measurement site under certain circumstances, such aswhen the first elongate portion 1006 is attached to an uneven or bumpyregion of the patient's skin, or to a measurement site that is otherwiserelatively difficult to attach to. For example, because the leg of thefirst end 1020 is centrally located and thus removed from the edges ofthe tape portions 1014, 1016, it can reduce the tendency for the firstelongate portion 1006 to peel-off of the patient. Moreover, thesingle-legged structure may have relatively less spring action orrestoring force than a multiple-legged structure, also reducing peel-offtendency.

In one use scenario, first end 1006 of the attachment element 1004including the single-legged first end 1020 of the backbone 1010 areplaced over the patient's Adam's apple, providing enhanced adhesion tothe relatively uneven Adam's apple region. In the example use scenario,the sensor assembly is further wrapped around the side of the patient'sneck such that the sensing element is positioned across the side of thefront of the patient's neck. Finally, the second end 1008 of theattachment element 1004 including the multi-legged structure of thesecond end 1022 of the backbone 1010 are placed generally on the side ofthe patient's neck, which is relatively less bumpy than the Adam's appleregion. In such a case, the forked structure of the elongate member 1010allows for both: (1) robust adhesion over the patient's Adam's apple dueto the single-legged structure of the first end 1020; and (2) improvedspring-like behavior in pressing the sensor against the measurement sitedue to the double-legged structure of the second end 1022.

In other embodiments, the first end 1020 may also be forked and theelongate member 1010 may generally comprise an “X” shape. One or more ofthe first and second ends 1020, 1022 may include more than two legs. Inyet other embodiments, both of the first and second ends 1020, 1022 mayinclude only one leg in a manner similar to the elongate member 910 ofFIG. 9.

Patient Anchor

Movements such as yanking, jerking or pulling of the cable may causestress on the adhesive connection between the sensor assembly 201 andthe patient. Such stress may be caused by movement of the patient,movement of the monitor, or accidental pulling on the cable by medicalpersonnel, for example. It can therefore be beneficial to secure thecable to the body at a point between the ends of the cable, therebydecoupling potential movement of the cable from the adhesive connectionbetween the sensor assembly 201 and the patient. As such, the cableassembly can include a patient anchor which advantageously secures thecable to the patient at a point between the ends of the cable. Thepatient anchor may include one or more panels which adhesively securethe cable to the body, for example.

FIG. 11A is a perspective view of a patient anchor 1100 according to oneembodiment of the disclosure. The patient anchor 1100 may be the patientanchor 203 of FIG. 2A or some other patient anchor. However, in someembodiments, the sensor assembly 201 does not include any patientanchor. The patient anchor may be referred to as forming part of a cableassembly. As shown, the patient anchor 1100 is attached to the sensorcable 1102 between a sensor subassembly (not shown) and a sensorconnector subassembly (not shown) such as one of the sensorsubassemblies and sensor connector subassemblies described herein. Aswill be described, the patient anchor 1100 advantageously provides aintermediate point of contact between the sensor assembly and thepatient, thereby reducing the stress on the point of contact between thepatient and the sensor subassembly. Such stress may be caused by jerkingor yanking of the cable 1102, for example. The patient anchor ispositioned on the cable 1102 between a proximal segment 1116 of thecable 1102 and a distal segment 1118 of the cable 1102. The proximalsegment 1116 terminates in a proximal end (not shown) configured toattach to the sensor subassembly and the distal segment 1118 terminatesin a distal end configured to connect to a sensor connector subassembly.

FIG. 11B is a perspective, exploded view of a patient anchor 1100according to one embodiment of the disclosure. Referring to FIGS. 11A-B,the patient anchor 1100 includes a top anchor panel 1104, a bottomanchor panel 1106, and a liner panel 1108. The top and bottom anchorpanels 1104, 1106 adhesively attach to opposing sides of the cable 1102and to each other while the liner panel 1108 adhesively attaches to theunderside of the bottom panel 1106. The underside 1110 of the linerpanel is removable from the bottom panel 1106 to reveal an adhesive onthe underside of the bottom panel 1106 which is configured to attach tothe patient's skin. In various embodiments, the panels 1106, 1108include rubber, plastic, tape, such as a cloth tape, foam tape, oradhesive film, or other compressible material that has adhesive on oneor both of their faces. The liner panel includes an adhesive film orother similar material.

As shown, the cable 1102 is straight at the points at which the cable1102 enters the patient anchor 1100. However, as shown in FIG. 11B, thecable 1102 includes a bent portion 1119 in the region in which thepatient anchor is attached. The shape of the bent portion 1119 furtherdecouples the proximal segment 1116, and thus the adhesive connectionbetween sensor assembly and the patient, from stress incident on thedistal segment 1118. This improved decoupling is achieved by providingone or more mechanical bends, such as the bends 1115, 1117, in the cable1102. The bent portion 1119 may also improve the attachment of the cable1102 to the panels 1104, 1106 by, for example, providing more cablesurface area for the panels 1104, 1106 to attach to. For example, in theillustrated embodiment, the bent portion 1119 is formed in the shape ofan “S.” The cable 1102 is bent before application of the anchor panels1104, 1106 which adhere to the cable 1102 and hold bent portion 1119 inplace, for example. The bent portion 1119 can be held in place in otherways. For example, in one embodiment, the bent portion 1119 of the cable1102 is relatively rigid.

FIG. 12 is a top view of a patient anchor 202 and a sensor subassembly1204 element attached to a patient according to one embodiment of thedisclosure. As shown with respect to a top cross-sectional view of apatient's neck 1208, the patient anchor 1202 is attached to the patient1208 at an intermediate point 1210 while the sensor subassembly 1204 isattached at the monitoring point 1212. As discussed, the patient anchoradvantageously reduces stress on the contact point 1212 between thesensor subassembly 1204 and the patient due, for example, to stress fromyanking or jerking on the cable 1206. While the patient anchor 1202 isshown attached to the patient's neck, the patient anchor 1202 may beattached elsewhere in some embodiments. For example, in oneconfiguration, the patient anchor 1202 is attached to the patient'supper chest. In various configurations, the anchor 1202 may be attachedto the shoulder, arm, or some other portion of the patient. In somecases, the anchor 1202 may be attached to an object other than thepatient. For example, the patient anchor 1202 can be attached to thepatient's bed or another generally fixed object.

A method of attaching a sensor to a measurement site using a patientanchor, such as the patient anchor 1100, for example includes attachingthe sensor to the measurement site. The method further includesattaching the patient anchor to an anchoring location a predetermineddistance from the measurement site. As discussed the patient anchor ispositioned between a proximal end of a cable coupled to the sensor and adistal end of a cable coupled to a sensor connector. The predetermineddistance may be selected such that the proximal segment 1118 of cable1006 between the sensor subassembly and the patient anchor 1100 providessome slack when the sensor assembly and patient anchor are attached,thereby avoiding any tension on the proximal segment 1118 and anyresulting stress on the adhesive connection between the patient and thesensor assembly. Moreover, the predetermined distance may be selected soas to provide a certain maximum amount of slack when the sensor assemblyand patient anchor are attached so that the proximal segment 1118 isunlikely to become snagged or pulled during use. The predetermineddistance of certain embodiments is also selected such that the length ofthe proximal segment 1118 is appropriate for attachment of the patientanchor 1002 to a portion of the body relatively well-suited forattachment to the patient anchor, such as a flat or hairless portion ofthe body. In various embodiments, the predetermined distance is frombetween about one inch and 12 inches and the length of the proximalsegment 1118 is from between 1.5 inches and 18 inches. In otherembodiments, the predetermined distance is from between about threeinches and six inches and the length of the proximal segment 1018 isfrom between about four inches and nine inches. In other embodiments,the predetermined distance is less than one inch or greater than 12inches.

In another embodiment, the patient anchor includes one integral pieceand does not include the separate panels 1106, 1108 and a liner 1110. Inanother embodiment, the bent portion 1118 may not be included, or may beformed into a different shape, such as an “L” shape, for example. Invarious embodiments, the bent portion 1118 may include any shape thatincludes one or more pre-formed bends, as described above, or whichotherwise decouple stress incident on the distal segment 1116 of thecable 1102 from the adhesive connection between the sensor assembly andthe patient. In addition, the proximal and distal ends may be configuredto connect to other components. For example, in other embodiments, thedistal end is configured to connect to a patient monitor or patientmonitor connector. Moreover, in some embodiments, the patient anchor1100 is attached to the patient or other object via a non-adhesivemechanism. For example, the patient anchor 1100 may comprise a clip orother mechanical attachment mechanism. In on embodiment the anchor 1100comprises an alligator type clip attachable to a patient's clothing.

An acoustic sensor has been described with respect to certainembodiments. Various combinations of the components and subcomponentsdescribed herein are within the scope of the disclosure. For example, incertain embodiments, one or more of the attachment subassembly, theauxiliary sensor, the acoustic coupler, the electrical shieldingbarrier, the bonding layer, the information element and patient anchorare not included. In one embodiment, for example, the sensor assemblyincludes all of the aforementioned components except for the auxiliarysensor and the patient anchor. In another embodiment, the sensorassembly includes all of the aforementioned components except for theinformation element.

Other combinations, omissions, substitutions and modifications arewithin the scope of the disclosure. It is contemplated that variousaspects and features of the systems and methods described can bepracticed separately, combined together, or substituted for one another,and that a variety of combination and sub combinations of the featuresand aspects can be made and still fall within the scope of thedisclosure. Furthermore, the systems described above need not includeall of the modules and functions described in the preferred embodiments.Accordingly, the present disclosure is not intended to be limited by therecitation of the preferred embodiments, but is to be defined byreference to the appended claims.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. Thus, such conditional language is not generally intended toimply that features, elements and/or states are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or states are included or are to beperformed in any particular embodiment.

Depending on the embodiment, certain acts, events, or functions of anyof the methods described herein can be performed in a differentsequence, can be added, merged, or left out all together (e.g., not alldescribed acts or events are necessary for the practice of the method).Moreover, in certain embodiments, acts or events can be performedconcurrently, e.g., through multi-threaded processing, interruptprocessing, or multiple processors or processor cores, rather thansequentially.

The various illustrative logical blocks, modules, circuits, andalgorithm steps described in connection with the embodiments disclosedherein can be implemented as electronic hardware, computer software, orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. The described functionalitycan be implemented in varying ways for each particular application, butsuch implementation decisions should not be interpreted as causing adeparture from the scope of the disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein can be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor can be a microprocessor, but in thealternative, the processor can be any conventional processor,controller, microcontroller, or state machine. A processor can also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The blocks of the methods and algorithms described in connection withthe embodiments disclosed herein can be embodied directly in hardware,in a software module executed by a processor, or in a combination of thetwo. A software module can reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, a hard disk, a removabledisk, a CD-ROM, or any other form of computer-readable storage mediumknown in the art. An exemplary storage medium is coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium can beintegral to the processor. The processor and the storage medium canreside in an ASIC. The ASIC can reside in a user terminal. In thealternative, the processor and the storage medium can reside as discretecomponents in a user terminal.

While the above detailed description has shown, described, and pointedout novel features as applied to various embodiments, it will beunderstood that various omissions, substitutions, and changes in theform and details of the devices or algorithms illustrated can be madewithout departing from the spirit of the disclosure. As will berecognized, certain embodiments of the inventions described herein canbe embodied within a form that does not provide all of the features andbenefits set forth herein, as some features can be used or practicedseparately from others. The scope of certain inventions disclosed hereinis indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

1. (canceled)
 2. An acoustic sensor assembly comprising: a frame atleast partially defining an open cavity; a sensing element configured tooutput a signal responsive to acoustic vibrations, the sensing elementsupported by the frame, at least a portion of the sensing elementcomprising a piezoelectric material that is stretched in tension acrossthe open cavity; electrical contacts electrically coupled with thesensing element and configured to convey an electrical signalcorresponding to the signal responsive to the acoustic vibrations, theelectrical contacts isolated from the open cavity by a physical barrier;and an acoustic coupler supported by the frame and including an innerprotrusion that extends into the open cavity and is positioned to applypressure to at least the portion of the sensing element that isstretched in tension across the open cavity to push a section of thesensing element into the open cavity both when the acoustic sensorassembly is attached to a medical patient and when the acoustic sensorassembly is not attached to the medical patient, the acoustic couplerconfigured to transmit acoustic vibrations to the sensing elementthrough the acoustic coupler when the acoustic sensor assembly isattached to the medical patient.
 3. The acoustic sensor assembly ofclaim 2, wherein the acoustic coupler further includes an outerprotrusion disposed on an outside surface of the acoustic coupler. 4.The acoustic sensor assembly of claim 2, wherein the acoustic couplerelectrically isolates the sensing element from the medical patient whenthe acoustic sensor assembly is attached to the medical patient.
 5. Theacoustic sensor assembly of claim 2, wherein the acoustic couplercomprises an elastomer.
 6. The acoustic sensor assembly of claim 2,wherein the acoustic coupler is configured to evenly distribute pressureon the sensing element.
 7. The acoustic sensor assembly of claim 2further comprising: an elongate member supported by the frame, theelongate member comprising a spring portion extending at least partiallybeyond opposite sides of the frame, wherein the elongate member isconfigured to apply a predetermined force to the frame with the springportion, wherein the acoustic sensor assembly is pressed against ameasurement site of the medical patient when the acoustic sensorassembly is attached to the medical patient.
 8. The acoustic sensorassembly of claim 7, wherein the predetermined force is determined atleast in part based upon a stiffness of the spring portion.
 9. Theacoustic sensor assembly of claim 2 further comprising: a resilientbackbone extending across and beyond opposite sides of the frame; andattachment elements provided at outside ends of said backbone, theattachment elements comprising top and bottom portions, wherein the topportion is attached to said backbone, the bottom portion is configuredto attach to a medical patient, and wherein the top portion isconfigured to be inclined with respect to said bottom portion whenattached to said medical patient.
 10. The acoustic sensor assembly ofclaim 2 further comprising an information element supported by theframe.
 11. The acoustic sensor assembly of claim 10, wherein theinformation element is configured to store sensor use information. 12.The acoustic sensor assembly of claim 10, wherein the informationelement is configured to store sensor compatibility information.
 13. Theacoustic sensor assembly of claim 10, wherein the information element isconfigured to store sensor calibration information.
 14. The acousticsensor assembly of claim 10 further comprising a cable in communicationwith the sensing element and a connector attached to the cable, whereinthe information element is supported by the connector.
 15. The acousticsensor assembly of claim 10, wherein the information element comprisesone or more memory devices.
 16. The acoustic sensor assembly of claim 2,further comprising an attachment element configured to apply apredetermined force to the frame during use.
 17. The acoustic sensorassembly of claim 16, wherein the attachment element includes anattachment layer, wherein the acoustic sensor assembly is attached tothe medical patient by attaching the attachment layer to the medicalpatient's skin, wherein said attaching the attachment layer comprisesmoving a portion of the attachment element from a first position inwhich the portion of the attachment element is substantially parallel tothe attachment layer to a second position in which the portion of theattachment element is inclined at an angle with respect to theattachment layer.
 18. The acoustic sensor assembly of claim 17, whereinthe portion of the attachment element is coupled to the attachment layerat a position near the attachment layer's center.
 19. A methodcomprising: using an acoustic sensor according to claim 2, attached to amedical patient, to provide a signal responsive to acoustic vibrationsindicative of one or more physiological parameters of the medicalpatient, the acoustic coupler being in contact with the medical patient;and outputting the signal based on acoustic vibrations transmittedthrough the acoustic coupler and detected by the sensing element. 20.The method of claim 19 further comprising using an attachment assemblyof the acoustic sensor configured to apply a predetermined force to theframe, wherein the acoustic sensor is pressed against the medicalpatient.
 21. A method of using an acoustic sensor according to claim 2,the acoustic sensor attached to a medical patient such that the acousticcoupler is pressed against the medical patient, the method comprising:receiving, via the acoustic coupler, acoustic vibrations; transmitting,via the acoustic coupler, the received acoustic vibrations to thesensing element; converting, via the sensing element, the transmittedacoustic vibrations into electrical signals; and providing theelectrical signals to the electrical contacts of the acoustic sensor.22. The method of claim 21, wherein applying the acoustic sensor to themedical patient causes the acoustic coupler to further push the sectionof the sensing element into the open cavity.